Fresh start

1 files changed, 5811 insertions, 0 deletions

diff --git a/jni/ruby/array.c b/jni/ruby/array.c
new file mode 100644
index 0000000..baa7193
--- /dev/null
+++ b/jni/ruby/array.c
@@ -0,0 +1,5811 @@
+/**********************************************************************
+
+  array.c -
+
+  $Author: nagachika $
+  created at: Fri Aug  6 09:46:12 JST 1993
+
+  Copyright (C) 1993-2007 Yukihiro Matsumoto
+  Copyright (C) 2000  Network Applied Communication Laboratory, Inc.
+  Copyright (C) 2000  Information-technology Promotion Agency, Japan
+
+**********************************************************************/
+
+#include "internal.h"
+#include "ruby/util.h"
+#include "ruby/st.h"
+#include "probes.h"
+#include "id.h"
+
+#ifndef ARRAY_DEBUG
+# define NDEBUG
+#endif
+#include <assert.h>
+
+VALUE rb_cArray;
+
+static ID id_cmp, id_div, id_power;
+
+#define ARY_DEFAULT_SIZE 16
+#define ARY_MAX_SIZE (LONG_MAX / (int)sizeof(VALUE))
+
+# define ARY_SHARED_P(ary) \
+    (assert(!FL_TEST((ary), ELTS_SHARED) || !FL_TEST((ary), RARRAY_EMBED_FLAG)), \
+     FL_TEST((ary),ELTS_SHARED)!=0)
+# define ARY_EMBED_P(ary) \
+    (assert(!FL_TEST((ary), ELTS_SHARED) || !FL_TEST((ary), RARRAY_EMBED_FLAG)), \
+     FL_TEST((ary), RARRAY_EMBED_FLAG)!=0)
+
+#define ARY_HEAP_PTR(a) (assert(!ARY_EMBED_P(a)), RARRAY(a)->as.heap.ptr)
+#define ARY_HEAP_LEN(a) (assert(!ARY_EMBED_P(a)), RARRAY(a)->as.heap.len)
+#define ARY_EMBED_PTR(a) (assert(ARY_EMBED_P(a)), RARRAY(a)->as.ary)
+#define ARY_EMBED_LEN(a) \
+    (assert(ARY_EMBED_P(a)), \
+     (long)((RBASIC(a)->flags >> RARRAY_EMBED_LEN_SHIFT) & \
+	 (RARRAY_EMBED_LEN_MASK >> RARRAY_EMBED_LEN_SHIFT)))
+#define ARY_HEAP_SIZE(a) (assert(!ARY_EMBED_P(a)), assert(ARY_OWNS_HEAP_P(a)), RARRAY(a)->as.heap.aux.capa * sizeof(VALUE))
+
+#define ARY_OWNS_HEAP_P(a) (!FL_TEST((a), ELTS_SHARED|RARRAY_EMBED_FLAG))
+#define FL_SET_EMBED(a) do { \
+    assert(!ARY_SHARED_P(a)); \
+    FL_SET((a), RARRAY_EMBED_FLAG); \
+} while (0)
+#define FL_UNSET_EMBED(ary) FL_UNSET((ary), RARRAY_EMBED_FLAG|RARRAY_EMBED_LEN_MASK)
+#define FL_SET_SHARED(ary) do { \
+    assert(!ARY_EMBED_P(ary)); \
+    FL_SET((ary), ELTS_SHARED); \
+} while (0)
+#define FL_UNSET_SHARED(ary) FL_UNSET((ary), ELTS_SHARED)
+
+#define ARY_SET_PTR(ary, p) do { \
+    assert(!ARY_EMBED_P(ary)); \
+    assert(!OBJ_FROZEN(ary)); \
+    RARRAY(ary)->as.heap.ptr = (p); \
+} while (0)
+#define ARY_SET_EMBED_LEN(ary, n) do { \
+    long tmp_n = (n); \
+    assert(ARY_EMBED_P(ary)); \
+    assert(!OBJ_FROZEN(ary)); \
+    RBASIC(ary)->flags &= ~RARRAY_EMBED_LEN_MASK; \
+    RBASIC(ary)->flags |= (tmp_n) << RARRAY_EMBED_LEN_SHIFT; \
+} while (0)
+#define ARY_SET_HEAP_LEN(ary, n) do { \
+    assert(!ARY_EMBED_P(ary)); \
+    RARRAY(ary)->as.heap.len = (n); \
+} while (0)
+#define ARY_SET_LEN(ary, n) do { \
+    if (ARY_EMBED_P(ary)) { \
+        ARY_SET_EMBED_LEN((ary), (n)); \
+    } \
+    else { \
+        ARY_SET_HEAP_LEN((ary), (n)); \
+    } \
+    assert(RARRAY_LEN(ary) == (n)); \
+} while (0)
+#define ARY_INCREASE_PTR(ary, n) do  { \
+    assert(!ARY_EMBED_P(ary)); \
+    assert(!OBJ_FROZEN(ary)); \
+    RARRAY(ary)->as.heap.ptr += (n); \
+} while (0)
+#define ARY_INCREASE_LEN(ary, n) do  { \
+    assert(!OBJ_FROZEN(ary)); \
+    if (ARY_EMBED_P(ary)) { \
+        ARY_SET_EMBED_LEN((ary), RARRAY_LEN(ary)+(n)); \
+    } \
+    else { \
+        RARRAY(ary)->as.heap.len += (n); \
+    } \
+} while (0)
+
+#define ARY_CAPA(ary) (ARY_EMBED_P(ary) ? RARRAY_EMBED_LEN_MAX : \
+		       ARY_SHARED_ROOT_P(ary) ? RARRAY_LEN(ary) : RARRAY(ary)->as.heap.aux.capa)
+#define ARY_SET_CAPA(ary, n) do { \
+    assert(!ARY_EMBED_P(ary)); \
+    assert(!ARY_SHARED_P(ary)); \
+    assert(!OBJ_FROZEN(ary)); \
+    RARRAY(ary)->as.heap.aux.capa = (n); \
+} while (0)
+
+#define ARY_SHARED(ary) (assert(ARY_SHARED_P(ary)), RARRAY(ary)->as.heap.aux.shared)
+#define ARY_SET_SHARED(ary, value) do { \
+    const VALUE _ary_ = (ary); \
+    const VALUE _value_ = (value); \
+    assert(!ARY_EMBED_P(_ary_)); \
+    assert(ARY_SHARED_P(_ary_)); \
+    assert(ARY_SHARED_ROOT_P(_value_)); \
+    RB_OBJ_WRITE(_ary_, &RARRAY(_ary_)->as.heap.aux.shared, _value_); \
+} while (0)
+#define RARRAY_SHARED_ROOT_FLAG FL_USER5
+#define ARY_SHARED_ROOT_P(ary) (FL_TEST((ary), RARRAY_SHARED_ROOT_FLAG))
+#define ARY_SHARED_NUM(ary) \
+    (assert(ARY_SHARED_ROOT_P(ary)), RARRAY(ary)->as.heap.aux.capa)
+#define ARY_SHARED_OCCUPIED(ary) (ARY_SHARED_NUM(ary) == 1)
+#define ARY_SET_SHARED_NUM(ary, value) do { \
+    assert(ARY_SHARED_ROOT_P(ary)); \
+    RARRAY(ary)->as.heap.aux.capa = (value); \
+} while (0)
+#define FL_SET_SHARED_ROOT(ary) do { \
+    assert(!ARY_EMBED_P(ary)); \
+    FL_SET((ary), RARRAY_SHARED_ROOT_FLAG); \
+} while (0)
+
+#define ARY_SET(a, i, v) RARRAY_ASET((assert(!ARY_SHARED_P(a)), (a)), (i), (v))
+
+void
+rb_mem_clear(register VALUE *mem, register long size)
+{
+    while (size--) {
+	*mem++ = Qnil;
+    }
+}
+
+static void
+ary_mem_clear(VALUE ary, long beg, long size)
+{
+    RARRAY_PTR_USE(ary, ptr, {
+	rb_mem_clear(ptr + beg, size);
+    });
+}
+
+static inline void
+memfill(register VALUE *mem, register long size, register VALUE val)
+{
+    while (size--) {
+	*mem++ = val;
+    }
+}
+
+static void
+ary_memfill(VALUE ary, long beg, long size, VALUE val)
+{
+    RARRAY_PTR_USE(ary, ptr, {
+	memfill(ptr + beg, size, val);
+	RB_OBJ_WRITTEN(ary, Qundef, val);
+    });
+}
+
+static void
+ary_memcpy0(VALUE ary, long beg, long argc, const VALUE *argv, VALUE buff_owner_ary)
+{
+#if 1
+    assert(!ARY_SHARED_P(buff_owner_ary));
+
+    if (argc > (int)(128/sizeof(VALUE)) /* is magic number (cache line size) */) {
+	rb_gc_writebarrier_remember(buff_owner_ary);
+	RARRAY_PTR_USE(ary, ptr, {
+	    MEMCPY(ptr+beg, argv, VALUE, argc);
+	});
+    }
+    else {
+	int i;
+	RARRAY_PTR_USE(ary, ptr, {
+	    for (i=0; i<argc; i++) {
+		RB_OBJ_WRITE(buff_owner_ary, &ptr[i+beg], argv[i]);
+	    }
+	});
+    }
+#else
+    /* giveup write barrier (traditional way) */
+    RARRAY_PTR(buff_owner_ary);
+    MEMCPY(RARRAY_PTR(ary)+beg, argv, VALUE, argc);
+#endif
+}
+
+static void
+ary_memcpy(VALUE ary, long beg, long argc, const VALUE *argv)
+{
+    ary_memcpy0(ary, beg, argc, argv, ary);
+}
+
+static void
+ary_resize_capa(VALUE ary, long capacity)
+{
+    assert(RARRAY_LEN(ary) <= capacity);
+    assert(!OBJ_FROZEN(ary));
+    assert(!ARY_SHARED_P(ary));
+    if (capacity > RARRAY_EMBED_LEN_MAX) {
+        if (ARY_EMBED_P(ary)) {
+            long len = ARY_EMBED_LEN(ary);
+            VALUE *ptr = ALLOC_N(VALUE, (capacity));
+            MEMCPY(ptr, ARY_EMBED_PTR(ary), VALUE, len);
+            FL_UNSET_EMBED(ary);
+            ARY_SET_PTR(ary, ptr);
+            ARY_SET_HEAP_LEN(ary, len);
+        }
+        else {
+	    SIZED_REALLOC_N(RARRAY(ary)->as.heap.ptr, VALUE, capacity, RARRAY(ary)->as.heap.aux.capa);
+        }
+        ARY_SET_CAPA(ary, (capacity));
+    }
+    else {
+        if (!ARY_EMBED_P(ary)) {
+            long len = RARRAY_LEN(ary);
+	    const VALUE *ptr = RARRAY_CONST_PTR(ary);
+
+	    if (len > capacity) len = capacity;
+            MEMCPY((VALUE *)RARRAY(ary)->as.ary, ptr, VALUE, len);
+            FL_SET_EMBED(ary);
+            ARY_SET_LEN(ary, len);
+	    ruby_xfree((VALUE *)ptr);
+        }
+    }
+}
+
+static inline void
+ary_shrink_capa(VALUE ary)
+{
+    long capacity = ARY_HEAP_LEN(ary);
+    long old_capa = RARRAY(ary)->as.heap.aux.capa;
+    assert(!ARY_SHARED_P(ary));
+    assert(old_capa >= capacity);
+    if (old_capa > capacity)
+	REALLOC_N(RARRAY(ary)->as.heap.ptr, VALUE, capacity);
+}
+
+static void
+ary_double_capa(VALUE ary, long min)
+{
+    long new_capa = ARY_CAPA(ary) / 2;
+
+    if (new_capa < ARY_DEFAULT_SIZE) {
+	new_capa = ARY_DEFAULT_SIZE;
+    }
+    if (new_capa >= ARY_MAX_SIZE - min) {
+	new_capa = (ARY_MAX_SIZE - min) / 2;
+    }
+    new_capa += min;
+    ary_resize_capa(ary, new_capa);
+}
+
+static void
+rb_ary_decrement_share(VALUE shared)
+{
+    if (shared) {
+	long num = ARY_SHARED_NUM(shared) - 1;
+	if (num == 0) {
+	    rb_ary_free(shared);
+	    rb_gc_force_recycle(shared);
+	}
+	else if (num > 0) {
+	    ARY_SET_SHARED_NUM(shared, num);
+	}
+    }
+}
+
+static void
+rb_ary_unshare(VALUE ary)
+{
+    VALUE shared = RARRAY(ary)->as.heap.aux.shared;
+    rb_ary_decrement_share(shared);
+    FL_UNSET_SHARED(ary);
+}
+
+static inline void
+rb_ary_unshare_safe(VALUE ary)
+{
+    if (ARY_SHARED_P(ary) && !ARY_EMBED_P(ary)) {
+	rb_ary_unshare(ary);
+    }
+}
+
+static VALUE
+rb_ary_increment_share(VALUE shared)
+{
+    long num = ARY_SHARED_NUM(shared);
+    if (num >= 0) {
+	ARY_SET_SHARED_NUM(shared, num + 1);
+    }
+    return shared;
+}
+
+static void
+rb_ary_set_shared(VALUE ary, VALUE shared)
+{
+    rb_ary_increment_share(shared);
+    FL_SET_SHARED(ary);
+    ARY_SET_SHARED(ary, shared);
+}
+
+static inline void
+rb_ary_modify_check(VALUE ary)
+{
+    rb_check_frozen(ary);
+}
+
+void
+rb_ary_modify(VALUE ary)
+{
+    rb_ary_modify_check(ary);
+    if (ARY_SHARED_P(ary)) {
+	long shared_len, len = RARRAY_LEN(ary);
+	VALUE shared = ARY_SHARED(ary);
+        if (len <= RARRAY_EMBED_LEN_MAX) {
+	    const VALUE *ptr = ARY_HEAP_PTR(ary);
+            FL_UNSET_SHARED(ary);
+            FL_SET_EMBED(ary);
+	    MEMCPY((VALUE *)ARY_EMBED_PTR(ary), ptr, VALUE, len);
+            rb_ary_decrement_share(shared);
+            ARY_SET_EMBED_LEN(ary, len);
+        }
+	else if (ARY_SHARED_OCCUPIED(shared) && len > ((shared_len = RARRAY_LEN(shared))>>1)) {
+	    long shift = RARRAY_CONST_PTR(ary) - RARRAY_CONST_PTR(shared);
+	    FL_UNSET_SHARED(ary);
+	    ARY_SET_PTR(ary, RARRAY_CONST_PTR(shared));
+	    ARY_SET_CAPA(ary, shared_len);
+	    RARRAY_PTR_USE(ary, ptr, {
+		MEMMOVE(ptr, ptr+shift, VALUE, len);
+	    });
+	    FL_SET_EMBED(shared);
+	    rb_ary_decrement_share(shared);
+	}
+        else {
+            VALUE *ptr = ALLOC_N(VALUE, len);
+            MEMCPY(ptr, RARRAY_CONST_PTR(ary), VALUE, len);
+            rb_ary_unshare(ary);
+            ARY_SET_CAPA(ary, len);
+            ARY_SET_PTR(ary, ptr);
+        }
+
+	rb_gc_writebarrier_remember(ary);
+    }
+}
+
+static VALUE
+ary_ensure_room_for_push(VALUE ary, long add_len)
+{
+    long old_len = RARRAY_LEN(ary);
+    long new_len = old_len + add_len;
+    long capa;
+
+    if (old_len > ARY_MAX_SIZE - add_len) {
+	rb_raise(rb_eIndexError, "index %ld too big", new_len);
+    }
+    if (ARY_SHARED_P(ary)) {
+	if (new_len > RARRAY_EMBED_LEN_MAX) {
+	    VALUE shared = ARY_SHARED(ary);
+	    if (ARY_SHARED_OCCUPIED(shared)) {
+		if (RARRAY_CONST_PTR(ary) - RARRAY_CONST_PTR(shared) + new_len <= RARRAY_LEN(shared)) {
+		    rb_ary_modify_check(ary);
+		    return shared;
+		}
+		else {
+		    /* if array is shared, then it is likely it participate in push/shift pattern */
+		    rb_ary_modify(ary);
+		    capa = ARY_CAPA(ary);
+		    if (new_len > capa - (capa >> 6)) {
+			ary_double_capa(ary, new_len);
+		    }
+		    return ary;
+		}
+	    }
+	}
+    }
+    rb_ary_modify(ary);
+    capa = ARY_CAPA(ary);
+    if (new_len > capa) {
+	ary_double_capa(ary, new_len);
+    }
+
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *      ary.freeze -> ary
+ *
+ *  Calls Object#freeze on +ary+ to prevent any further
+ *  modification. A RuntimeError will be raised if a modification
+ *  attempt is made.
+ *
+ */
+
+VALUE
+rb_ary_freeze(VALUE ary)
+{
+    return rb_obj_freeze(ary);
+}
+
+/*
+ *  call-seq:
+ *     ary.frozen?  -> true or false
+ *
+ *  Return +true+ if this array is frozen (or temporarily frozen
+ *  while being sorted). See also Object#frozen?
+ */
+
+static VALUE
+rb_ary_frozen_p(VALUE ary)
+{
+    if (OBJ_FROZEN(ary)) return Qtrue;
+    return Qfalse;
+}
+
+/* This can be used to take a snapshot of an array (with
+   e.g. rb_ary_replace) and check later whether the array has been
+   modified from the snapshot.  The snapshot is cheap, though if
+   something does modify the array it will pay the cost of copying
+   it.  If Array#pop or Array#shift has been called, the array will
+   be still shared with the snapshot, but the array length will
+   differ. */
+VALUE
+rb_ary_shared_with_p(VALUE ary1, VALUE ary2)
+{
+    if (!ARY_EMBED_P(ary1) && ARY_SHARED_P(ary1) &&
+	!ARY_EMBED_P(ary2) && ARY_SHARED_P(ary2) &&
+	RARRAY(ary1)->as.heap.aux.shared == RARRAY(ary2)->as.heap.aux.shared &&
+	RARRAY(ary1)->as.heap.len == RARRAY(ary2)->as.heap.len) {
+	return Qtrue;
+    }
+    return Qfalse;
+}
+
+static VALUE
+ary_alloc(VALUE klass)
+{
+    NEWOBJ_OF(ary, struct RArray, klass, T_ARRAY | RARRAY_EMBED_FLAG | (RGENGC_WB_PROTECTED_ARRAY ? FL_WB_PROTECTED : 0));
+    /* Created array is:
+     *   FL_SET_EMBED((VALUE)ary);
+     *   ARY_SET_EMBED_LEN((VALUE)ary, 0);
+     */
+    return (VALUE)ary;
+}
+
+static VALUE
+empty_ary_alloc(VALUE klass)
+{
+    if (RUBY_DTRACE_ARRAY_CREATE_ENABLED()) {
+	RUBY_DTRACE_ARRAY_CREATE(0, rb_sourcefile(), rb_sourceline());
+    }
+
+    return ary_alloc(klass);
+}
+
+static VALUE
+ary_new(VALUE klass, long capa)
+{
+    VALUE ary,*ptr;
+
+    if (capa < 0) {
+	rb_raise(rb_eArgError, "negative array size (or size too big)");
+    }
+    if (capa > ARY_MAX_SIZE) {
+	rb_raise(rb_eArgError, "array size too big");
+    }
+
+    if (RUBY_DTRACE_ARRAY_CREATE_ENABLED()) {
+	RUBY_DTRACE_ARRAY_CREATE(capa, rb_sourcefile(), rb_sourceline());
+    }
+
+    ary = ary_alloc(klass);
+    if (capa > RARRAY_EMBED_LEN_MAX) {
+	ptr = ALLOC_N(VALUE, capa);
+        FL_UNSET_EMBED(ary);
+        ARY_SET_PTR(ary, ptr);
+        ARY_SET_CAPA(ary, capa);
+        ARY_SET_HEAP_LEN(ary, 0);
+    }
+
+    return ary;
+}
+
+VALUE
+rb_ary_new_capa(long capa)
+{
+    return ary_new(rb_cArray, capa);
+}
+
+VALUE
+rb_ary_new(void)
+{
+    return rb_ary_new2(RARRAY_EMBED_LEN_MAX);
+}
+
+VALUE
+(rb_ary_new_from_args)(long n, ...)
+{
+    va_list ar;
+    VALUE ary;
+    long i;
+
+    ary = rb_ary_new2(n);
+
+    va_start(ar, n);
+    for (i=0; i<n; i++) {
+	ARY_SET(ary, i, va_arg(ar, VALUE));
+    }
+    va_end(ar);
+
+    ARY_SET_LEN(ary, n);
+    return ary;
+}
+
+VALUE
+rb_ary_new_from_values(long n, const VALUE *elts)
+{
+    VALUE ary;
+
+    ary = rb_ary_new2(n);
+    if (n > 0 && elts) {
+	ary_memcpy(ary, 0, n, elts);
+	ARY_SET_LEN(ary, n);
+    }
+
+    return ary;
+}
+
+VALUE
+rb_ary_tmp_new(long capa)
+{
+    return ary_new(0, capa);
+}
+
+VALUE
+rb_ary_tmp_new_fill(long capa)
+{
+    VALUE ary = ary_new(0, capa);
+    ary_memfill(ary, 0, capa, Qnil);
+    ARY_SET_LEN(ary, capa);
+    return ary;
+}
+
+void
+rb_ary_free(VALUE ary)
+{
+    if (ARY_OWNS_HEAP_P(ary)) {
+	ruby_sized_xfree((void *)ARY_HEAP_PTR(ary), ARY_HEAP_SIZE(ary));
+    }
+}
+
+RUBY_FUNC_EXPORTED size_t
+rb_ary_memsize(VALUE ary)
+{
+    if (ARY_OWNS_HEAP_P(ary)) {
+	return RARRAY(ary)->as.heap.aux.capa * sizeof(VALUE);
+    }
+    else {
+	return 0;
+    }
+}
+
+static inline void
+ary_discard(VALUE ary)
+{
+    rb_ary_free(ary);
+    RBASIC(ary)->flags |= RARRAY_EMBED_FLAG;
+    RBASIC(ary)->flags &= ~RARRAY_EMBED_LEN_MASK;
+}
+
+static VALUE
+ary_make_shared(VALUE ary)
+{
+    assert(!ARY_EMBED_P(ary));
+    if (ARY_SHARED_P(ary)) {
+	return ARY_SHARED(ary);
+    }
+    else if (ARY_SHARED_ROOT_P(ary)) {
+	return ary;
+    }
+    else if (OBJ_FROZEN(ary)) {
+	ary_shrink_capa(ary);
+	FL_SET_SHARED_ROOT(ary);
+	ARY_SET_SHARED_NUM(ary, 1);
+	return ary;
+    }
+    else {
+	long capa = ARY_CAPA(ary), len = RARRAY_LEN(ary);
+	NEWOBJ_OF(shared, struct RArray, 0, T_ARRAY | (RGENGC_WB_PROTECTED_ARRAY ? FL_WB_PROTECTED : 0));
+        FL_UNSET_EMBED(shared);
+
+	ARY_SET_LEN((VALUE)shared, capa);
+	ARY_SET_PTR((VALUE)shared, RARRAY_CONST_PTR(ary));
+	ary_mem_clear((VALUE)shared, len, capa - len);
+	FL_SET_SHARED_ROOT(shared);
+	ARY_SET_SHARED_NUM((VALUE)shared, 1);
+	FL_SET_SHARED(ary);
+	ARY_SET_SHARED(ary, (VALUE)shared);
+	OBJ_FREEZE(shared);
+	return (VALUE)shared;
+    }
+}
+
+static VALUE
+ary_make_substitution(VALUE ary)
+{
+    long len = RARRAY_LEN(ary);
+
+    if (len <= RARRAY_EMBED_LEN_MAX) {
+	VALUE subst = rb_ary_new2(len);
+	ary_memcpy(subst, 0, len, RARRAY_CONST_PTR(ary));
+        ARY_SET_EMBED_LEN(subst, len);
+        return subst;
+    }
+    else {
+        return rb_ary_increment_share(ary_make_shared(ary));
+    }
+}
+
+VALUE
+rb_assoc_new(VALUE car, VALUE cdr)
+{
+    return rb_ary_new3(2, car, cdr);
+}
+
+static VALUE
+to_ary(VALUE ary)
+{
+    return rb_convert_type(ary, T_ARRAY, "Array", "to_ary");
+}
+
+VALUE
+rb_check_array_type(VALUE ary)
+{
+    return rb_check_convert_type(ary, T_ARRAY, "Array", "to_ary");
+}
+
+/*
+ *  call-seq:
+ *     Array.try_convert(obj) -> array or nil
+ *
+ *  Tries to convert +obj+ into an array, using +to_ary+ method.  Returns the
+ *  converted array or +nil+ if +obj+ cannot be converted for any reason.
+ *  This method can be used to check if an argument is an array.
+ *
+ *     Array.try_convert([1])   #=> [1]
+ *     Array.try_convert("1")   #=> nil
+ *
+ *     if tmp = Array.try_convert(arg)
+ *       # the argument is an array
+ *     elsif tmp = String.try_convert(arg)
+ *       # the argument is a string
+ *     end
+ *
+ */
+
+static VALUE
+rb_ary_s_try_convert(VALUE dummy, VALUE ary)
+{
+    return rb_check_array_type(ary);
+}
+
+/*
+ *  call-seq:
+ *     Array.new(size=0, default=nil)
+ *     Array.new(array)
+ *     Array.new(size) {|index| block }
+ *
+ *  Returns a new array.
+ *
+ *  In the first form, if no arguments are sent, the new array will be empty.
+ *  When a +size+ and an optional +default+ are sent, an array is created with
+ *  +size+ copies of +default+.  Take notice that all elements will reference the
+ *  same object +default+.
+ *
+ *  The second form creates a copy of the array passed as a parameter (the
+ *  array is generated by calling to_ary on the parameter).
+ *
+ *    first_array = ["Matz", "Guido"]
+ *
+ *    second_array = Array.new(first_array) #=> ["Matz", "Guido"]
+ *
+ *    first_array.equal? second_array       #=> false
+ *
+ *  In the last form, an array of the given size is created.  Each element in
+ *  this array is created by passing the element's index to the given block
+ *  and storing the return value.
+ *
+ *    Array.new(3){ |index| index ** 2 }
+ *    # => [0, 1, 4]
+ *
+ *  == Common gotchas
+ *
+ *  When sending the second parameter, the same object will be used as the
+ *  value for all the array elements:
+ *
+ *     a = Array.new(2, Hash.new)
+ *     # => [{}, {}]
+ *
+ *     a[0]['cat'] = 'feline'
+ *     a # => [{"cat"=>"feline"}, {"cat"=>"feline"}]
+ *
+ *     a[1]['cat'] = 'Felix'
+ *     a # => [{"cat"=>"Felix"}, {"cat"=>"Felix"}]
+ *
+ *  Since all the Array elements store the same hash, changes to one of them
+ *  will affect them all.
+ *
+ *  If multiple copies are what you want, you should use the block
+ *  version which uses the result of that block each time an element
+ *  of the array needs to be initialized:
+ *
+ *     a = Array.new(2) { Hash.new }
+ *     a[0]['cat'] = 'feline'
+ *     a # => [{"cat"=>"feline"}, {}]
+ *
+ */
+
+static VALUE
+rb_ary_initialize(int argc, VALUE *argv, VALUE ary)
+{
+    long len;
+    VALUE size, val;
+
+    rb_ary_modify(ary);
+    if (argc == 0) {
+	if (ARY_OWNS_HEAP_P(ary) && RARRAY_CONST_PTR(ary) != 0) {
+	    ruby_sized_xfree((void *)RARRAY_CONST_PTR(ary), ARY_HEAP_SIZE(ary));
+	}
+        rb_ary_unshare_safe(ary);
+        FL_SET_EMBED(ary);
+	ARY_SET_EMBED_LEN(ary, 0);
+	if (rb_block_given_p()) {
+	    rb_warning("given block not used");
+	}
+	return ary;
+    }
+    rb_scan_args(argc, argv, "02", &size, &val);
+    if (argc == 1 && !FIXNUM_P(size)) {
+	val = rb_check_array_type(size);
+	if (!NIL_P(val)) {
+	    rb_ary_replace(ary, val);
+	    return ary;
+	}
+    }
+
+    len = NUM2LONG(size);
+    /* NUM2LONG() may call size.to_int, ary can be frozen, modified, etc */
+    if (len < 0) {
+	rb_raise(rb_eArgError, "negative array size");
+    }
+    if (len > ARY_MAX_SIZE) {
+	rb_raise(rb_eArgError, "array size too big");
+    }
+    /* recheck after argument conversion */
+    rb_ary_modify(ary);
+    ary_resize_capa(ary, len);
+    if (rb_block_given_p()) {
+	long i;
+
+	if (argc == 2) {
+	    rb_warn("block supersedes default value argument");
+	}
+	for (i=0; i<len; i++) {
+	    rb_ary_store(ary, i, rb_yield(LONG2NUM(i)));
+	    ARY_SET_LEN(ary, i + 1);
+	}
+    }
+    else {
+	ary_memfill(ary, 0, len, val);
+	ARY_SET_LEN(ary, len);
+    }
+    return ary;
+}
+
+/*
+ * Returns a new array populated with the given objects.
+ *
+ *   Array.[]( 1, 'a', /^A/ ) # => [1, "a", /^A/]
+ *   Array[ 1, 'a', /^A/ ]    # => [1, "a", /^A/]
+ *   [ 1, 'a', /^A/ ]         # => [1, "a", /^A/]
+ */
+
+static VALUE
+rb_ary_s_create(int argc, VALUE *argv, VALUE klass)
+{
+    VALUE ary = ary_new(klass, argc);
+    if (argc > 0 && argv) {
+        ary_memcpy(ary, 0, argc, argv);
+        ARY_SET_LEN(ary, argc);
+    }
+
+    return ary;
+}
+
+void
+rb_ary_store(VALUE ary, long idx, VALUE val)
+{
+    long len = RARRAY_LEN(ary);
+
+    if (idx < 0) {
+	idx += len;
+	if (idx < 0) {
+	    rb_raise(rb_eIndexError, "index %ld too small for array; minimum: %ld",
+		     idx - len, -len);
+	}
+    }
+    else if (idx >= ARY_MAX_SIZE) {
+	rb_raise(rb_eIndexError, "index %ld too big", idx);
+    }
+
+    rb_ary_modify(ary);
+    if (idx >= ARY_CAPA(ary)) {
+	ary_double_capa(ary, idx);
+    }
+    if (idx > len) {
+	ary_mem_clear(ary, len, idx - len + 1);
+    }
+
+    if (idx >= len) {
+	ARY_SET_LEN(ary, idx + 1);
+    }
+    ARY_SET(ary, idx, val);
+}
+
+static VALUE
+ary_make_partial(VALUE ary, VALUE klass, long offset, long len)
+{
+    assert(offset >= 0);
+    assert(len >= 0);
+    assert(offset+len <= RARRAY_LEN(ary));
+
+    if (len <= RARRAY_EMBED_LEN_MAX) {
+        VALUE result = ary_alloc(klass);
+	ary_memcpy(result, 0, len, RARRAY_CONST_PTR(ary) + offset);
+        ARY_SET_EMBED_LEN(result, len);
+        return result;
+    }
+    else {
+        VALUE shared, result = ary_alloc(klass);
+        FL_UNSET_EMBED(result);
+
+        shared = ary_make_shared(ary);
+        ARY_SET_PTR(result, RARRAY_CONST_PTR(ary));
+        ARY_SET_LEN(result, RARRAY_LEN(ary));
+        rb_ary_set_shared(result, shared);
+
+        ARY_INCREASE_PTR(result, offset);
+        ARY_SET_LEN(result, len);
+        return result;
+    }
+}
+
+static VALUE
+ary_make_shared_copy(VALUE ary)
+{
+    return ary_make_partial(ary, rb_obj_class(ary), 0, RARRAY_LEN(ary));
+}
+
+enum ary_take_pos_flags
+{
+    ARY_TAKE_FIRST = 0,
+    ARY_TAKE_LAST = 1
+};
+
+static VALUE
+ary_take_first_or_last(int argc, const VALUE *argv, VALUE ary, enum ary_take_pos_flags last)
+{
+    VALUE nv;
+    long n;
+    long len;
+    long offset = 0;
+
+    rb_scan_args(argc, argv, "1", &nv);
+    n = NUM2LONG(nv);
+    len = RARRAY_LEN(ary);
+    if (n > len) {
+	n = len;
+    }
+    else if (n < 0) {
+	rb_raise(rb_eArgError, "negative array size");
+    }
+    if (last) {
+	offset = len - n;
+    }
+    return ary_make_partial(ary, rb_cArray, offset, n);
+}
+
+/*
+ *  call-seq:
+ *     ary << obj            -> ary
+ *
+ *  Append---Pushes the given object on to the end of this array. This
+ *  expression returns the array itself, so several appends
+ *  may be chained together.
+ *
+ *     [ 1, 2 ] << "c" << "d" << [ 3, 4 ]
+ *             #=>  [ 1, 2, "c", "d", [ 3, 4 ] ]
+ *
+ */
+
+VALUE
+rb_ary_push(VALUE ary, VALUE item)
+{
+    long idx = RARRAY_LEN(ary);
+    VALUE target_ary = ary_ensure_room_for_push(ary, 1);
+    RARRAY_PTR_USE(ary, ptr, {
+	RB_OBJ_WRITE(target_ary, &ptr[idx], item);
+    });
+    ARY_SET_LEN(ary, idx + 1);
+    return ary;
+}
+
+VALUE
+rb_ary_cat(VALUE ary, const VALUE *argv, long len)
+{
+    long oldlen = RARRAY_LEN(ary);
+    VALUE target_ary = ary_ensure_room_for_push(ary, len);
+    ary_memcpy0(ary, oldlen, len, argv, target_ary);
+    ARY_SET_LEN(ary, oldlen + len);
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.push(obj, ... )   -> ary
+ *
+ *  Append --- Pushes the given object(s) on to the end of this array. This
+ *  expression returns the array itself, so several appends
+ *  may be chained together. See also Array#pop for the opposite
+ *  effect.
+ *
+ *     a = [ "a", "b", "c" ]
+ *     a.push("d", "e", "f")
+ *             #=> ["a", "b", "c", "d", "e", "f"]
+ *     [1, 2, 3,].push(4).push(5)
+ *             #=> [1, 2, 3, 4, 5]
+ */
+
+static VALUE
+rb_ary_push_m(int argc, VALUE *argv, VALUE ary)
+{
+    return rb_ary_cat(ary, argv, argc);
+}
+
+VALUE
+rb_ary_pop(VALUE ary)
+{
+    long n;
+    rb_ary_modify_check(ary);
+    n = RARRAY_LEN(ary);
+    if (n == 0) return Qnil;
+    if (ARY_OWNS_HEAP_P(ary) &&
+	n * 3 < ARY_CAPA(ary) &&
+	ARY_CAPA(ary) > ARY_DEFAULT_SIZE)
+    {
+	ary_resize_capa(ary, n * 2);
+    }
+    --n;
+    ARY_SET_LEN(ary, n);
+    return RARRAY_AREF(ary, n);
+}
+
+/*
+ *  call-seq:
+ *     ary.pop    -> obj or nil
+ *     ary.pop(n) -> new_ary
+ *
+ *  Removes the last element from +self+ and returns it, or
+ *  +nil+ if the array is empty.
+ *
+ *  If a number +n+ is given, returns an array of the last +n+ elements
+ *  (or less) just like <code>array.slice!(-n, n)</code> does. See also
+ *  Array#push for the opposite effect.
+ *
+ *     a = [ "a", "b", "c", "d" ]
+ *     a.pop     #=> "d"
+ *     a.pop(2)  #=> ["b", "c"]
+ *     a         #=> ["a"]
+ */
+
+static VALUE
+rb_ary_pop_m(int argc, VALUE *argv, VALUE ary)
+{
+    VALUE result;
+
+    if (argc == 0) {
+	return rb_ary_pop(ary);
+    }
+
+    rb_ary_modify_check(ary);
+    result = ary_take_first_or_last(argc, argv, ary, ARY_TAKE_LAST);
+    ARY_INCREASE_LEN(ary, -RARRAY_LEN(result));
+    return result;
+}
+
+VALUE
+rb_ary_shift(VALUE ary)
+{
+    VALUE top;
+    long len = RARRAY_LEN(ary);
+
+    rb_ary_modify_check(ary);
+    if (len == 0) return Qnil;
+    top = RARRAY_AREF(ary, 0);
+    if (!ARY_SHARED_P(ary)) {
+	if (len < ARY_DEFAULT_SIZE) {
+	    RARRAY_PTR_USE(ary, ptr, {
+		MEMMOVE(ptr, ptr+1, VALUE, len-1);
+	    }); /* WB: no new reference */
+            ARY_INCREASE_LEN(ary, -1);
+	    return top;
+	}
+        assert(!ARY_EMBED_P(ary)); /* ARY_EMBED_LEN_MAX < ARY_DEFAULT_SIZE */
+
+	ARY_SET(ary, 0, Qnil);
+	ary_make_shared(ary);
+    }
+    else if (ARY_SHARED_OCCUPIED(ARY_SHARED(ary))) {
+	RARRAY_PTR_USE(ary, ptr, ptr[0] = Qnil);
+    }
+    ARY_INCREASE_PTR(ary, 1);		/* shift ptr */
+    ARY_INCREASE_LEN(ary, -1);
+
+    return top;
+}
+
+/*
+ *  call-seq:
+ *     ary.shift    -> obj or nil
+ *     ary.shift(n) -> new_ary
+ *
+ *  Removes the first element of +self+ and returns it (shifting all
+ *  other elements down by one). Returns +nil+ if the array
+ *  is empty.
+ *
+ *  If a number +n+ is given, returns an array of the first +n+ elements
+ *  (or less) just like <code>array.slice!(0, n)</code> does. With +ary+
+ *  containing only the remainder elements, not including what was shifted to
+ *  +new_ary+. See also Array#unshift for the opposite effect.
+ *
+ *     args = [ "-m", "-q", "filename" ]
+ *     args.shift     #=> "-m"
+ *     args           #=> ["-q", "filename"]
+ *
+ *     args = [ "-m", "-q", "filename" ]
+ *     args.shift(2)  #=> ["-m", "-q"]
+ *     args           #=> ["filename"]
+ */
+
+static VALUE
+rb_ary_shift_m(int argc, VALUE *argv, VALUE ary)
+{
+    VALUE result;
+    long n;
+
+    if (argc == 0) {
+	return rb_ary_shift(ary);
+    }
+
+    rb_ary_modify_check(ary);
+    result = ary_take_first_or_last(argc, argv, ary, ARY_TAKE_FIRST);
+    n = RARRAY_LEN(result);
+    if (ARY_SHARED_P(ary)) {
+	if (ARY_SHARED_OCCUPIED(ARY_SHARED(ary))) {
+	    ary_mem_clear(ary, 0, n);
+	}
+        ARY_INCREASE_PTR(ary, n);
+    }
+    else {
+	RARRAY_PTR_USE(ary, ptr, {
+	    MEMMOVE(ptr, ptr + n, VALUE, RARRAY_LEN(ary)-n);
+	}); /* WB: no new reference */
+    }
+    ARY_INCREASE_LEN(ary, -n);
+
+    return result;
+}
+
+static VALUE
+ary_ensure_room_for_unshift(VALUE ary, int argc)
+{
+    long len = RARRAY_LEN(ary);
+    long new_len = len + argc;
+    long capa;
+    const VALUE *head, *sharedp;
+
+    if (len > ARY_MAX_SIZE - argc) {
+	rb_raise(rb_eIndexError, "index %ld too big", new_len);
+    }
+
+    if (ARY_SHARED_P(ary)) {
+	VALUE shared = ARY_SHARED(ary);
+	capa = RARRAY_LEN(shared);
+	if (ARY_SHARED_OCCUPIED(shared) && capa > new_len) {
+	    head = RARRAY_CONST_PTR(ary);
+	    sharedp = RARRAY_CONST_PTR(shared);
+	    goto makeroom_if_need;
+	}
+    }
+
+    rb_ary_modify(ary);
+    capa = ARY_CAPA(ary);
+    if (capa - (capa >> 6) <= new_len) {
+	ary_double_capa(ary, new_len);
+    }
+
+    /* use shared array for big "queues" */
+    if (new_len > ARY_DEFAULT_SIZE * 4) {
+	/* make a room for unshifted items */
+	capa = ARY_CAPA(ary);
+	ary_make_shared(ary);
+
+	head = sharedp = RARRAY_CONST_PTR(ary);
+	goto makeroom;
+      makeroom_if_need:
+	if (head - sharedp < argc) {
+	    long room;
+	  makeroom:
+	    room = capa - new_len;
+	    room -= room >> 4;
+	    MEMMOVE((VALUE *)sharedp + argc + room, head, VALUE, len);
+	    head = sharedp + argc + room;
+	}
+	ARY_SET_PTR(ary, head - argc);
+	assert(ARY_SHARED_OCCUPIED(ARY_SHARED(ary)));
+	return ARY_SHARED(ary);
+    }
+    else {
+	/* sliding items */
+	RARRAY_PTR_USE(ary, ptr, {
+	    MEMMOVE(ptr + argc, ptr, VALUE, len);
+	});
+
+	return ary;
+    }
+}
+
+/*
+ *  call-seq:
+ *     ary.unshift(obj, ...)  -> ary
+ *
+ *  Prepends objects to the front of +self+, moving other elements upwards.
+ *  See also Array#shift for the opposite effect.
+ *
+ *     a = [ "b", "c", "d" ]
+ *     a.unshift("a")   #=> ["a", "b", "c", "d"]
+ *     a.unshift(1, 2)  #=> [ 1, 2, "a", "b", "c", "d"]
+ */
+
+static VALUE
+rb_ary_unshift_m(int argc, VALUE *argv, VALUE ary)
+{
+    long len = RARRAY_LEN(ary);
+    VALUE target_ary;
+
+    if (argc == 0) {
+	rb_ary_modify_check(ary);
+	return ary;
+    }
+
+    target_ary = ary_ensure_room_for_unshift(ary, argc);
+    ary_memcpy0(ary, 0, argc, argv, target_ary);
+    ARY_SET_LEN(ary, len + argc);
+    return ary;
+}
+
+VALUE
+rb_ary_unshift(VALUE ary, VALUE item)
+{
+    return rb_ary_unshift_m(1,&item,ary);
+}
+
+/* faster version - use this if you don't need to treat negative offset */
+static inline VALUE
+rb_ary_elt(VALUE ary, long offset)
+{
+    long len = RARRAY_LEN(ary);
+    if (len == 0) return Qnil;
+    if (offset < 0 || len <= offset) {
+	return Qnil;
+    }
+    return RARRAY_AREF(ary, offset);
+}
+
+VALUE
+rb_ary_entry(VALUE ary, long offset)
+{
+    if (offset < 0) {
+	offset += RARRAY_LEN(ary);
+    }
+    return rb_ary_elt(ary, offset);
+}
+
+VALUE
+rb_ary_subseq(VALUE ary, long beg, long len)
+{
+    VALUE klass;
+    long alen = RARRAY_LEN(ary);
+
+    if (beg > alen) return Qnil;
+    if (beg < 0 || len < 0) return Qnil;
+
+    if (alen < len || alen < beg + len) {
+	len = alen - beg;
+    }
+    klass = rb_obj_class(ary);
+    if (len == 0) return ary_new(klass, 0);
+
+    return ary_make_partial(ary, klass, beg, len);
+}
+
+/*
+ *  call-seq:
+ *     ary[index]                -> obj     or nil
+ *     ary[start, length]        -> new_ary or nil
+ *     ary[range]                -> new_ary or nil
+ *     ary.slice(index)          -> obj     or nil
+ *     ary.slice(start, length)  -> new_ary or nil
+ *     ary.slice(range)          -> new_ary or nil
+ *
+ *  Element Reference --- Returns the element at +index+, or returns a
+ *  subarray starting at the +start+ index and continuing for +length+
+ *  elements, or returns a subarray specified by +range+ of indices.
+ *
+ *  Negative indices count backward from the end of the array (-1 is the last
+ *  element).  For +start+ and +range+ cases the starting index is just before
+ *  an element.  Additionally, an empty array is returned when the starting
+ *  index for an element range is at the end of the array.
+ *
+ *  Returns +nil+ if the index (or starting index) are out of range.
+ *
+ *     a = [ "a", "b", "c", "d", "e" ]
+ *     a[2] +  a[0] + a[1]    #=> "cab"
+ *     a[6]                   #=> nil
+ *     a[1, 2]                #=> [ "b", "c" ]
+ *     a[1..3]                #=> [ "b", "c", "d" ]
+ *     a[4..7]                #=> [ "e" ]
+ *     a[6..10]               #=> nil
+ *     a[-3, 3]               #=> [ "c", "d", "e" ]
+ *     # special cases
+ *     a[5]                   #=> nil
+ *     a[6, 1]                #=> nil
+ *     a[5, 1]                #=> []
+ *     a[5..10]               #=> []
+ *
+ */
+
+VALUE
+rb_ary_aref(int argc, const VALUE *argv, VALUE ary)
+{
+    VALUE arg;
+    long beg, len;
+
+    if (argc == 2) {
+	beg = NUM2LONG(argv[0]);
+	len = NUM2LONG(argv[1]);
+	if (beg < 0) {
+	    beg += RARRAY_LEN(ary);
+	}
+	return rb_ary_subseq(ary, beg, len);
+    }
+    if (argc != 1) {
+	rb_scan_args(argc, argv, "11", NULL, NULL);
+    }
+    arg = argv[0];
+    /* special case - speeding up */
+    if (FIXNUM_P(arg)) {
+	return rb_ary_entry(ary, FIX2LONG(arg));
+    }
+    /* check if idx is Range */
+    switch (rb_range_beg_len(arg, &beg, &len, RARRAY_LEN(ary), 0)) {
+      case Qfalse:
+	break;
+      case Qnil:
+	return Qnil;
+      default:
+	return rb_ary_subseq(ary, beg, len);
+    }
+    return rb_ary_entry(ary, NUM2LONG(arg));
+}
+
+/*
+ *  call-seq:
+ *     ary.at(index)   ->   obj  or nil
+ *
+ *  Returns the element at +index+. A negative index counts from the end of
+ *  +self+. Returns +nil+ if the index is out of range. See also
+ *  Array#[].
+ *
+ *     a = [ "a", "b", "c", "d", "e" ]
+ *     a.at(0)     #=> "a"
+ *     a.at(-1)    #=> "e"
+ */
+
+static VALUE
+rb_ary_at(VALUE ary, VALUE pos)
+{
+    return rb_ary_entry(ary, NUM2LONG(pos));
+}
+
+/*
+ *  call-seq:
+ *     ary.first     ->   obj or nil
+ *     ary.first(n)  ->   new_ary
+ *
+ *  Returns the first element, or the first +n+ elements, of the array.
+ *  If the array is empty, the first form returns +nil+, and the
+ *  second form returns an empty array. See also Array#last for
+ *  the opposite effect.
+ *
+ *     a = [ "q", "r", "s", "t" ]
+ *     a.first     #=> "q"
+ *     a.first(2)  #=> ["q", "r"]
+ */
+
+static VALUE
+rb_ary_first(int argc, VALUE *argv, VALUE ary)
+{
+    if (argc == 0) {
+	if (RARRAY_LEN(ary) == 0) return Qnil;
+	return RARRAY_AREF(ary, 0);
+    }
+    else {
+	return ary_take_first_or_last(argc, argv, ary, ARY_TAKE_FIRST);
+    }
+}
+
+/*
+ *  call-seq:
+ *     ary.last     ->  obj or nil
+ *     ary.last(n)  ->  new_ary
+ *
+ *  Returns the last element(s) of +self+. If the array is empty,
+ *  the first form returns +nil+.
+ *
+ *  See also Array#first for the opposite effect.
+ *
+ *     a = [ "w", "x", "y", "z" ]
+ *     a.last     #=> "z"
+ *     a.last(2)  #=> ["y", "z"]
+ */
+
+VALUE
+rb_ary_last(int argc, const VALUE *argv, VALUE ary)
+{
+    if (argc == 0) {
+	long len = RARRAY_LEN(ary);
+	if (len == 0) return Qnil;
+	return RARRAY_AREF(ary, len-1);
+    }
+    else {
+	return ary_take_first_or_last(argc, argv, ary, ARY_TAKE_LAST);
+    }
+}
+
+/*
+ *  call-seq:
+ *     ary.fetch(index)                    -> obj
+ *     ary.fetch(index, default)           -> obj
+ *     ary.fetch(index) { |index| block }  -> obj
+ *
+ *  Tries to return the element at position +index+, but throws an IndexError
+ *  exception if the referenced +index+ lies outside of the array bounds.  This
+ *  error can be prevented by supplying a second argument, which will act as a
+ *  +default+ value.
+ *
+ *  Alternatively, if a block is given it will only be executed when an
+ *  invalid +index+ is referenced.  Negative values of +index+ count from the
+ *  end of the array.
+ *
+ *     a = [ 11, 22, 33, 44 ]
+ *     a.fetch(1)               #=> 22
+ *     a.fetch(-1)              #=> 44
+ *     a.fetch(4, 'cat')        #=> "cat"
+ *     a.fetch(100) { |i| puts "#{i} is out of bounds" }
+ *                              #=> "100 is out of bounds"
+ */
+
+static VALUE
+rb_ary_fetch(int argc, VALUE *argv, VALUE ary)
+{
+    VALUE pos, ifnone;
+    long block_given;
+    long idx;
+
+    rb_scan_args(argc, argv, "11", &pos, &ifnone);
+    block_given = rb_block_given_p();
+    if (block_given && argc == 2) {
+	rb_warn("block supersedes default value argument");
+    }
+    idx = NUM2LONG(pos);
+
+    if (idx < 0) {
+	idx +=  RARRAY_LEN(ary);
+    }
+    if (idx < 0 || RARRAY_LEN(ary) <= idx) {
+	if (block_given) return rb_yield(pos);
+	if (argc == 1) {
+	    rb_raise(rb_eIndexError, "index %ld outside of array bounds: %ld...%ld",
+			idx - (idx < 0 ? RARRAY_LEN(ary) : 0), -RARRAY_LEN(ary), RARRAY_LEN(ary));
+	}
+	return ifnone;
+    }
+    return RARRAY_AREF(ary, idx);
+}
+
+/*
+ *  call-seq:
+ *     ary.find_index(obj)             ->  int or nil
+ *     ary.find_index { |item| block } ->  int or nil
+ *     ary.find_index                  ->  Enumerator
+ *     ary.index(obj)             ->  int or nil
+ *     ary.index { |item| block } ->  int or nil
+ *     ary.index                  ->  Enumerator
+ *
+ *  Returns the _index_ of the first object in +ary+ such that the object is
+ *  <code>==</code> to +obj+.
+ *
+ *  If a block is given instead of an argument, returns the _index_ of the
+ *  first object for which the block returns +true+.  Returns +nil+ if no
+ *  match is found.
+ *
+ *  See also Array#rindex.
+ *
+ *  An Enumerator is returned if neither a block nor argument is given.
+ *
+ *     a = [ "a", "b", "c" ]
+ *     a.index("b")              #=> 1
+ *     a.index("z")              #=> nil
+ *     a.index { |x| x == "b" }  #=> 1
+ */
+
+static VALUE
+rb_ary_index(int argc, VALUE *argv, VALUE ary)
+{
+    const VALUE *ptr;
+    VALUE val;
+    long i, len;
+
+    if (argc == 0) {
+	RETURN_ENUMERATOR(ary, 0, 0);
+	for (i=0; i<RARRAY_LEN(ary); i++) {
+	    if (RTEST(rb_yield(RARRAY_AREF(ary, i)))) {
+		return LONG2NUM(i);
+	    }
+	}
+	return Qnil;
+    }
+    rb_check_arity(argc, 0, 1);
+    val = argv[0];
+    if (rb_block_given_p())
+	rb_warn("given block not used");
+    len = RARRAY_LEN(ary);
+    ptr = RARRAY_CONST_PTR(ary);
+    for (i=0; i<len; i++) {
+	VALUE e = ptr[i];
+	switch (rb_equal_opt(e, val)) {
+	  case Qundef:
+	    if (!rb_equal(e, val)) break;
+	  case Qtrue:
+	    return LONG2NUM(i);
+	  case Qfalse:
+	    continue;
+	}
+	len = RARRAY_LEN(ary);
+	ptr = RARRAY_CONST_PTR(ary);
+    }
+    return Qnil;
+}
+
+/*
+ *  call-seq:
+ *     ary.rindex(obj)             ->  int or nil
+ *     ary.rindex { |item| block } ->  int or nil
+ *     ary.rindex                  ->  Enumerator
+ *
+ *  Returns the _index_ of the last object in +self+ <code>==</code> to +obj+.
+ *
+ *  If a block is given instead of an argument, returns the _index_ of the
+ *  first object for which the block returns +true+, starting from the last
+ *  object.
+ *
+ *  Returns +nil+ if no match is found.
+ *
+ *  See also Array#index.
+ *
+ *  If neither block nor argument is given, an Enumerator is returned instead.
+ *
+ *     a = [ "a", "b", "b", "b", "c" ]
+ *     a.rindex("b")             #=> 3
+ *     a.rindex("z")             #=> nil
+ *     a.rindex { |x| x == "b" } #=> 3
+ */
+
+static VALUE
+rb_ary_rindex(int argc, VALUE *argv, VALUE ary)
+{
+    const VALUE *ptr;
+    VALUE val;
+    long i = RARRAY_LEN(ary), len;
+
+    if (argc == 0) {
+	RETURN_ENUMERATOR(ary, 0, 0);
+	while (i--) {
+	    if (RTEST(rb_yield(RARRAY_AREF(ary, i))))
+		return LONG2NUM(i);
+	    if (i > (len = RARRAY_LEN(ary))) {
+		i = len;
+	    }
+	}
+	return Qnil;
+    }
+    rb_check_arity(argc, 0, 1);
+    val = argv[0];
+    if (rb_block_given_p())
+	rb_warn("given block not used");
+    ptr = RARRAY_CONST_PTR(ary);
+    while (i--) {
+	VALUE e = ptr[i];
+	switch (rb_equal_opt(e, val)) {
+	  case Qundef:
+	    if (!rb_equal(e, val)) break;
+	  case Qtrue:
+	    return LONG2NUM(i);
+	  case Qfalse:
+	    continue;
+	}
+	if (i > (len = RARRAY_LEN(ary))) {
+	    i = len;
+	}
+	ptr = RARRAY_CONST_PTR(ary);
+    }
+    return Qnil;
+}
+
+VALUE
+rb_ary_to_ary(VALUE obj)
+{
+    VALUE tmp = rb_check_array_type(obj);
+
+    if (!NIL_P(tmp)) return tmp;
+    return rb_ary_new3(1, obj);
+}
+
+static void
+rb_ary_splice(VALUE ary, long beg, long len, VALUE rpl)
+{
+    long rlen;
+    long olen;
+
+    if (len < 0) rb_raise(rb_eIndexError, "negative length (%ld)", len);
+    olen = RARRAY_LEN(ary);
+    if (beg < 0) {
+	beg += olen;
+	if (beg < 0) {
+	    rb_raise(rb_eIndexError, "index %ld too small for array; minimum: %ld",
+		     beg - olen, -olen);
+	}
+    }
+    if (olen < len || olen < beg + len) {
+	len = olen - beg;
+    }
+
+    if (rpl == Qundef) {
+	rlen = 0;
+    }
+    else {
+	rpl = rb_ary_to_ary(rpl);
+	rlen = RARRAY_LEN(rpl);
+	olen = RARRAY_LEN(ary);	/* ary may be resized in rpl.to_ary too */
+    }
+    if (beg >= olen) {
+	VALUE target_ary;
+	if (beg > ARY_MAX_SIZE - rlen) {
+	    rb_raise(rb_eIndexError, "index %ld too big", beg);
+	}
+	target_ary = ary_ensure_room_for_push(ary, rlen-len); /* len is 0 or negative */
+	len = beg + rlen;
+	ary_mem_clear(ary, olen, beg - olen);
+	if (rlen > 0) {
+	    ary_memcpy0(ary, beg, rlen, RARRAY_CONST_PTR(rpl), target_ary);
+	}
+	ARY_SET_LEN(ary, len);
+    }
+    else {
+	long alen;
+
+	if (olen - len > ARY_MAX_SIZE - rlen) {
+	    rb_raise(rb_eIndexError, "index %ld too big", olen + rlen - len);
+	}
+	rb_ary_modify(ary);
+	alen = olen + rlen - len;
+	if (alen >= ARY_CAPA(ary)) {
+	    ary_double_capa(ary, alen);
+	}
+
+	if (len != rlen) {
+	    RARRAY_PTR_USE(ary, ptr,
+			   MEMMOVE(ptr + beg + rlen, ptr + beg + len,
+				   VALUE, olen - (beg + len)));
+	    ARY_SET_LEN(ary, alen);
+	}
+	if (rlen > 0) {
+	    MEMMOVE(RARRAY_PTR(ary) + beg, RARRAY_CONST_PTR(rpl), VALUE, rlen);
+	}
+    }
+    RB_GC_GUARD(rpl);
+}
+
+void
+rb_ary_set_len(VALUE ary, long len)
+{
+    long capa;
+
+    rb_ary_modify_check(ary);
+    if (ARY_SHARED_P(ary)) {
+	rb_raise(rb_eRuntimeError, "can't set length of shared ");
+    }
+    if (len > (capa = (long)ARY_CAPA(ary))) {
+	rb_bug("probable buffer overflow: %ld for %ld", len, capa);
+    }
+    ARY_SET_LEN(ary, len);
+}
+
+/*!
+ * expands or shrinks \a ary to \a len elements.
+ * expanded region will be filled with Qnil.
+ * \param ary  an array
+ * \param len  new size
+ * \return     \a ary
+ * \post       the size of \a ary is \a len.
+ */
+VALUE
+rb_ary_resize(VALUE ary, long len)
+{
+    long olen;
+
+    rb_ary_modify(ary);
+    olen = RARRAY_LEN(ary);
+    if (len == olen) return ary;
+    if (len > ARY_MAX_SIZE) {
+	rb_raise(rb_eIndexError, "index %ld too big", len);
+    }
+    if (len > olen) {
+	if (len >= ARY_CAPA(ary)) {
+	    ary_double_capa(ary, len);
+	}
+	ary_mem_clear(ary, olen, len - olen);
+	ARY_SET_LEN(ary, len);
+    }
+    else if (ARY_EMBED_P(ary)) {
+        ARY_SET_EMBED_LEN(ary, len);
+    }
+    else if (len <= RARRAY_EMBED_LEN_MAX) {
+	VALUE tmp[RARRAY_EMBED_LEN_MAX];
+	MEMCPY(tmp, ARY_HEAP_PTR(ary), VALUE, len);
+	ary_discard(ary);
+	MEMCPY((VALUE *)ARY_EMBED_PTR(ary), tmp, VALUE, len); /* WB: no new reference */
+        ARY_SET_EMBED_LEN(ary, len);
+    }
+    else {
+	if (olen > len + ARY_DEFAULT_SIZE) {
+	    SIZED_REALLOC_N(RARRAY(ary)->as.heap.ptr, VALUE, len, RARRAY(ary)->as.heap.aux.capa);
+	    ARY_SET_CAPA(ary, len);
+	}
+	ARY_SET_HEAP_LEN(ary, len);
+    }
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary[index]         = obj                      ->  obj
+ *     ary[start, length] = obj or other_ary or nil  ->  obj or other_ary or nil
+ *     ary[range]         = obj or other_ary or nil  ->  obj or other_ary or nil
+ *
+ *  Element Assignment --- Sets the element at +index+, or replaces a subarray
+ *  from the +start+ index for +length+ elements, or replaces a subarray
+ *  specified by the +range+ of indices.
+ *
+ *  If indices are greater than the current capacity of the array, the array
+ *  grows automatically.  Elements are inserted into the array at +start+ if
+ *  +length+ is zero.
+ *
+ *  Negative indices will count backward from the end of the array.  For
+ *  +start+ and +range+ cases the starting index is just before an element.
+ *
+ *  An IndexError is raised if a negative index points past the beginning of
+ *  the array.
+ *
+ *  See also Array#push, and Array#unshift.
+ *
+ *     a = Array.new
+ *     a[4] = "4";                 #=> [nil, nil, nil, nil, "4"]
+ *     a[0, 3] = [ 'a', 'b', 'c' ] #=> ["a", "b", "c", nil, "4"]
+ *     a[1..2] = [ 1, 2 ]          #=> ["a", 1, 2, nil, "4"]
+ *     a[0, 2] = "?"               #=> ["?", 2, nil, "4"]
+ *     a[0..2] = "A"               #=> ["A", "4"]
+ *     a[-1]   = "Z"               #=> ["A", "Z"]
+ *     a[1..-1] = nil              #=> ["A", nil]
+ *     a[1..-1] = []               #=> ["A"]
+ *     a[0, 0] = [ 1, 2 ]          #=> [1, 2, "A"]
+ *     a[3, 0] = "B"               #=> [1, 2, "A", "B"]
+ */
+
+static VALUE
+rb_ary_aset(int argc, VALUE *argv, VALUE ary)
+{
+    long offset, beg, len;
+
+    if (argc == 3) {
+	rb_ary_modify_check(ary);
+	beg = NUM2LONG(argv[0]);
+	len = NUM2LONG(argv[1]);
+	rb_ary_splice(ary, beg, len, argv[2]);
+	return argv[2];
+    }
+    rb_check_arity(argc, 2, 2);
+    rb_ary_modify_check(ary);
+    if (FIXNUM_P(argv[0])) {
+	offset = FIX2LONG(argv[0]);
+	goto fixnum;
+    }
+    if (rb_range_beg_len(argv[0], &beg, &len, RARRAY_LEN(ary), 1)) {
+	/* check if idx is Range */
+	rb_ary_splice(ary, beg, len, argv[1]);
+	return argv[1];
+    }
+
+    offset = NUM2LONG(argv[0]);
+fixnum:
+    rb_ary_store(ary, offset, argv[1]);
+    return argv[1];
+}
+
+/*
+ *  call-seq:
+ *     ary.insert(index, obj...)  -> ary
+ *
+ *  Inserts the given values before the element with the given +index+.
+ *
+ *  Negative indices count backwards from the end of the array, where +-1+ is
+ *  the last element. If a negative index is used, the given values will be
+ *  inserted after that element, so using an index of +-1+ will insert the
+ *  values at the end of the array.
+ *
+ *     a = %w{ a b c d }
+ *     a.insert(2, 99)         #=> ["a", "b", 99, "c", "d"]
+ *     a.insert(-2, 1, 2, 3)   #=> ["a", "b", 99, "c", 1, 2, 3, "d"]
+ */
+
+static VALUE
+rb_ary_insert(int argc, VALUE *argv, VALUE ary)
+{
+    long pos;
+
+    rb_check_arity(argc, 1, UNLIMITED_ARGUMENTS);
+    rb_ary_modify_check(ary);
+    if (argc == 1) return ary;
+    pos = NUM2LONG(argv[0]);
+    if (pos == -1) {
+	pos = RARRAY_LEN(ary);
+    }
+    if (pos < 0) {
+	pos++;
+    }
+    rb_ary_splice(ary, pos, 0, rb_ary_new4(argc - 1, argv + 1));
+    return ary;
+}
+
+static VALUE
+rb_ary_length(VALUE ary);
+
+static VALUE
+ary_enum_length(VALUE ary, VALUE args, VALUE eobj)
+{
+    return rb_ary_length(ary);
+}
+
+/*
+ *  call-seq:
+ *     ary.each { |item| block }  -> ary
+ *     ary.each                   -> Enumerator
+ *
+ *  Calls the given block once for each element in +self+, passing that element
+ *  as a parameter.
+ *
+ *  An Enumerator is returned if no block is given.
+ *
+ *     a = [ "a", "b", "c" ]
+ *     a.each {|x| print x, " -- " }
+ *
+ *  produces:
+ *
+ *     a -- b -- c --
+ */
+
+VALUE
+rb_ary_each(VALUE array)
+{
+    long i;
+    volatile VALUE ary = array;
+
+    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
+    for (i=0; i<RARRAY_LEN(ary); i++) {
+	rb_yield(RARRAY_AREF(ary, i));
+    }
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.each_index { |index| block }  -> ary
+ *     ary.each_index                    -> Enumerator
+ *
+ *  Same as Array#each, but passes the +index+ of the element instead of the
+ *  element itself.
+ *
+ *  An Enumerator is returned if no block is given.
+ *
+ *     a = [ "a", "b", "c" ]
+ *     a.each_index {|x| print x, " -- " }
+ *
+ *  produces:
+ *
+ *     0 -- 1 -- 2 --
+ */
+
+static VALUE
+rb_ary_each_index(VALUE ary)
+{
+    long i;
+    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
+
+    for (i=0; i<RARRAY_LEN(ary); i++) {
+	rb_yield(LONG2NUM(i));
+    }
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.reverse_each { |item| block }  -> ary
+ *     ary.reverse_each                   -> Enumerator
+ *
+ *  Same as Array#each, but traverses +self+ in reverse order.
+ *
+ *     a = [ "a", "b", "c" ]
+ *     a.reverse_each {|x| print x, " " }
+ *
+ *  produces:
+ *
+ *     c b a
+ */
+
+static VALUE
+rb_ary_reverse_each(VALUE ary)
+{
+    long len;
+
+    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
+    len = RARRAY_LEN(ary);
+    while (len--) {
+	long nlen;
+	rb_yield(RARRAY_AREF(ary, len));
+	nlen = RARRAY_LEN(ary);
+	if (nlen < len) {
+	    len = nlen;
+	}
+    }
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.length -> int
+ *
+ *  Returns the number of elements in +self+. May be zero.
+ *
+ *     [ 1, 2, 3, 4, 5 ].length   #=> 5
+ *     [].length                  #=> 0
+ */
+
+static VALUE
+rb_ary_length(VALUE ary)
+{
+    long len = RARRAY_LEN(ary);
+    return LONG2NUM(len);
+}
+
+/*
+ *  call-seq:
+ *     ary.empty?   -> true or false
+ *
+ *  Returns +true+ if +self+ contains no elements.
+ *
+ *     [].empty?   #=> true
+ */
+
+static VALUE
+rb_ary_empty_p(VALUE ary)
+{
+    if (RARRAY_LEN(ary) == 0)
+	return Qtrue;
+    return Qfalse;
+}
+
+VALUE
+rb_ary_dup(VALUE ary)
+{
+    long len = RARRAY_LEN(ary);
+    VALUE dup = rb_ary_new2(len);
+    ary_memcpy(dup, 0, len, RARRAY_CONST_PTR(ary));
+    ARY_SET_LEN(dup, len);
+    return dup;
+}
+
+VALUE
+rb_ary_resurrect(VALUE ary)
+{
+    return rb_ary_new4(RARRAY_LEN(ary), RARRAY_CONST_PTR(ary));
+}
+
+extern VALUE rb_output_fs;
+
+static void ary_join_1(VALUE obj, VALUE ary, VALUE sep, long i, VALUE result, int *first);
+
+static VALUE
+recursive_join(VALUE obj, VALUE argp, int recur)
+{
+    VALUE *arg = (VALUE *)argp;
+    VALUE ary = arg[0];
+    VALUE sep = arg[1];
+    VALUE result = arg[2];
+    int *first = (int *)arg[3];
+
+    if (recur) {
+	rb_raise(rb_eArgError, "recursive array join");
+    }
+    else {
+	ary_join_1(obj, ary, sep, 0, result, first);
+    }
+    return Qnil;
+}
+
+static void
+ary_join_0(VALUE ary, VALUE sep, long max, VALUE result)
+{
+    long i;
+    VALUE val;
+
+    if (max > 0) rb_enc_copy(result, RARRAY_AREF(ary, 0));
+    for (i=0; i<max; i++) {
+	val = RARRAY_AREF(ary, i);
+	if (i > 0 && !NIL_P(sep))
+	    rb_str_buf_append(result, sep);
+	rb_str_buf_append(result, val);
+	if (OBJ_TAINTED(val)) OBJ_TAINT(result);
+    }
+}
+
+static void
+ary_join_1(VALUE obj, VALUE ary, VALUE sep, long i, VALUE result, int *first)
+{
+    VALUE val, tmp;
+
+    for (; i<RARRAY_LEN(ary); i++) {
+	if (i > 0 && !NIL_P(sep))
+	    rb_str_buf_append(result, sep);
+
+	val = RARRAY_AREF(ary, i);
+	if (RB_TYPE_P(val, T_STRING)) {
+	  str_join:
+	    rb_str_buf_append(result, val);
+	    *first = FALSE;
+	}
+	else if (RB_TYPE_P(val, T_ARRAY)) {
+	    obj = val;
+	  ary_join:
+	    if (val == ary) {
+		rb_raise(rb_eArgError, "recursive array join");
+	    }
+	    else {
+		VALUE args[4];
+
+		args[0] = val;
+		args[1] = sep;
+		args[2] = result;
+		args[3] = (VALUE)first;
+		rb_exec_recursive(recursive_join, obj, (VALUE)args);
+	    }
+	}
+	else {
+	    tmp = rb_check_string_type(val);
+	    if (!NIL_P(tmp)) {
+		val = tmp;
+		goto str_join;
+	    }
+	    tmp = rb_check_convert_type(val, T_ARRAY, "Array", "to_ary");
+	    if (!NIL_P(tmp)) {
+		obj = val;
+		val = tmp;
+		goto ary_join;
+	    }
+	    val = rb_obj_as_string(val);
+	    if (*first) {
+		rb_enc_copy(result, val);
+		*first = FALSE;
+	    }
+	    goto str_join;
+	}
+    }
+}
+
+VALUE
+rb_ary_join(VALUE ary, VALUE sep)
+{
+    long len = 1, i;
+    int taint = FALSE;
+    VALUE val, tmp, result;
+
+    if (RARRAY_LEN(ary) == 0) return rb_usascii_str_new(0, 0);
+    if (OBJ_TAINTED(ary)) taint = TRUE;
+
+    if (!NIL_P(sep)) {
+	StringValue(sep);
+	len += RSTRING_LEN(sep) * (RARRAY_LEN(ary) - 1);
+    }
+    for (i=0; i<RARRAY_LEN(ary); i++) {
+	val = RARRAY_AREF(ary, i);
+	tmp = rb_check_string_type(val);
+
+	if (NIL_P(tmp) || tmp != val) {
+	    int first;
+	    result = rb_str_buf_new(len + (RARRAY_LEN(ary)-i)*10);
+	    rb_enc_associate(result, rb_usascii_encoding());
+	    if (taint) OBJ_TAINT(result);
+	    ary_join_0(ary, sep, i, result);
+	    first = i == 0;
+	    ary_join_1(ary, ary, sep, i, result, &first);
+	    return result;
+	}
+
+	len += RSTRING_LEN(tmp);
+    }
+
+    result = rb_str_buf_new(len);
+    if (taint) OBJ_TAINT(result);
+    ary_join_0(ary, sep, RARRAY_LEN(ary), result);
+
+    return result;
+}
+
+/*
+ *  call-seq:
+ *     ary.join(separator=$,)    -> str
+ *
+ *  Returns a string created by converting each element of the array to
+ *  a string, separated by the given +separator+.
+ *  If the +separator+ is +nil+, it uses current $,.
+ *  If both the +separator+ and $, are nil, it uses empty string.
+ *
+ *     [ "a", "b", "c" ].join        #=> "abc"
+ *     [ "a", "b", "c" ].join("-")   #=> "a-b-c"
+ */
+
+static VALUE
+rb_ary_join_m(int argc, VALUE *argv, VALUE ary)
+{
+    VALUE sep;
+
+    rb_scan_args(argc, argv, "01", &sep);
+    if (NIL_P(sep)) sep = rb_output_fs;
+
+    return rb_ary_join(ary, sep);
+}
+
+static VALUE
+inspect_ary(VALUE ary, VALUE dummy, int recur)
+{
+    int tainted = OBJ_TAINTED(ary);
+    long i;
+    VALUE s, str;
+
+    if (recur) return rb_usascii_str_new_cstr("[...]");
+    str = rb_str_buf_new2("[");
+    for (i=0; i<RARRAY_LEN(ary); i++) {
+	s = rb_inspect(RARRAY_AREF(ary, i));
+	if (OBJ_TAINTED(s)) tainted = TRUE;
+	if (i > 0) rb_str_buf_cat2(str, ", ");
+	else rb_enc_copy(str, s);
+	rb_str_buf_append(str, s);
+    }
+    rb_str_buf_cat2(str, "]");
+    if (tainted) OBJ_TAINT(str);
+    return str;
+}
+
+/*
+ *  call-seq:
+ *     ary.inspect  -> string
+ *     ary.to_s     -> string
+ *
+ *  Creates a string representation of +self+.
+ *
+ *     [ "a", "b", "c" ].to_s     #=> "[\"a\", \"b\", \"c\"]"
+ */
+
+static VALUE
+rb_ary_inspect(VALUE ary)
+{
+    if (RARRAY_LEN(ary) == 0) return rb_usascii_str_new2("[]");
+    return rb_exec_recursive(inspect_ary, ary, 0);
+}
+
+VALUE
+rb_ary_to_s(VALUE ary)
+{
+    return rb_ary_inspect(ary);
+}
+
+/*
+ *  call-seq:
+ *     ary.to_a     -> ary
+ *
+ *  Returns +self+.
+ *
+ *  If called on a subclass of Array, converts the receiver to an Array object.
+ */
+
+static VALUE
+rb_ary_to_a(VALUE ary)
+{
+    if (rb_obj_class(ary) != rb_cArray) {
+	VALUE dup = rb_ary_new2(RARRAY_LEN(ary));
+	rb_ary_replace(dup, ary);
+	return dup;
+    }
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.to_h     -> hash
+ *
+ *  Returns the result of interpreting <i>ary</i> as an array of
+ *  <tt>[key, value]</tt> pairs.
+ *
+ *     [[:foo, :bar], [1, 2]].to_h
+ *       # => {:foo => :bar, 1 => 2}
+ */
+
+static VALUE
+rb_ary_to_h(VALUE ary)
+{
+    long i;
+    VALUE hash = rb_hash_new();
+    for (i=0; i<RARRAY_LEN(ary); i++) {
+	VALUE key_value_pair = rb_check_array_type(rb_ary_elt(ary, i));
+	if (NIL_P(key_value_pair)) {
+	    rb_raise(rb_eTypeError, "wrong element type %s at %ld (expected array)",
+		rb_builtin_class_name(rb_ary_elt(ary, i)), i);
+	}
+	if (RARRAY_LEN(key_value_pair) != 2) {
+	    rb_raise(rb_eArgError, "wrong array length at %ld (expected 2, was %ld)",
+		i, RARRAY_LEN(key_value_pair));
+	}
+	rb_hash_aset(hash, RARRAY_AREF(key_value_pair, 0), RARRAY_AREF(key_value_pair, 1));
+    }
+    return hash;
+}
+
+/*
+ *  call-seq:
+ *     ary.to_ary -> ary
+ *
+ *  Returns +self+.
+ */
+
+static VALUE
+rb_ary_to_ary_m(VALUE ary)
+{
+    return ary;
+}
+
+static void
+ary_reverse(VALUE *p1, VALUE *p2)
+{
+    while (p1 < p2) {
+	VALUE tmp = *p1;
+	*p1++ = *p2;
+	*p2-- = tmp;
+    }
+}
+
+VALUE
+rb_ary_reverse(VALUE ary)
+{
+    VALUE *p2;
+    long len = RARRAY_LEN(ary);
+
+    rb_ary_modify(ary);
+    if (len > 1) {
+	RARRAY_PTR_USE(ary, p1, {
+	    p2 = p1 + len - 1;	/* points last item */
+	    ary_reverse(p1, p2);
+	}); /* WB: no new reference */
+    }
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.reverse!   -> ary
+ *
+ *  Reverses +self+ in place.
+ *
+ *     a = [ "a", "b", "c" ]
+ *     a.reverse!       #=> ["c", "b", "a"]
+ *     a                #=> ["c", "b", "a"]
+ */
+
+static VALUE
+rb_ary_reverse_bang(VALUE ary)
+{
+    return rb_ary_reverse(ary);
+}
+
+/*
+ *  call-seq:
+ *     ary.reverse    -> new_ary
+ *
+ *  Returns a new array containing +self+'s elements in reverse order.
+ *
+ *     [ "a", "b", "c" ].reverse   #=> ["c", "b", "a"]
+ *     [ 1 ].reverse               #=> [1]
+ */
+
+static VALUE
+rb_ary_reverse_m(VALUE ary)
+{
+    long len = RARRAY_LEN(ary);
+    VALUE dup = rb_ary_new2(len);
+
+    if (len > 0) {
+	const VALUE *p1 = RARRAY_CONST_PTR(ary);
+	VALUE *p2 = (VALUE *)RARRAY_CONST_PTR(dup) + len - 1;
+	do *p2-- = *p1++; while (--len > 0);
+    }
+    ARY_SET_LEN(dup, RARRAY_LEN(ary));
+    return dup;
+}
+
+static inline long
+rotate_count(long cnt, long len)
+{
+    return (cnt < 0) ? (len - (~cnt % len) - 1) : (cnt % len);
+}
+
+VALUE
+rb_ary_rotate(VALUE ary, long cnt)
+{
+    rb_ary_modify(ary);
+
+    if (cnt != 0) {
+	VALUE *ptr = RARRAY_PTR(ary);
+	long len = RARRAY_LEN(ary);
+
+	if (len > 0 && (cnt = rotate_count(cnt, len)) > 0) {
+	    --len;
+	    if (cnt < len) ary_reverse(ptr + cnt, ptr + len);
+	    if (--cnt > 0) ary_reverse(ptr, ptr + cnt);
+	    if (len > 0) ary_reverse(ptr, ptr + len);
+	    return ary;
+	}
+    }
+
+    return Qnil;
+}
+
+/*
+ *  call-seq:
+ *     ary.rotate!(count=1)   -> ary
+ *
+ *  Rotates +self+ in place so that the element at +count+ comes first, and
+ *  returns +self+.
+ *
+ *  If +count+ is negative then it rotates in the opposite direction, starting
+ *  from the end of the array where +-1+ is the last element.
+ *
+ *     a = [ "a", "b", "c", "d" ]
+ *     a.rotate!        #=> ["b", "c", "d", "a"]
+ *     a                #=> ["b", "c", "d", "a"]
+ *     a.rotate!(2)     #=> ["d", "a", "b", "c"]
+ *     a.rotate!(-3)    #=> ["a", "b", "c", "d"]
+ */
+
+static VALUE
+rb_ary_rotate_bang(int argc, VALUE *argv, VALUE ary)
+{
+    long n = 1;
+
+    switch (argc) {
+      case 1: n = NUM2LONG(argv[0]);
+      case 0: break;
+      default: rb_scan_args(argc, argv, "01", NULL);
+    }
+    rb_ary_rotate(ary, n);
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.rotate(count=1)    -> new_ary
+ *
+ *  Returns a new array by rotating +self+ so that the element at +count+ is
+ *  the first element of the new array.
+ *
+ *  If +count+ is negative then it rotates in the opposite direction, starting
+ *  from the end of +self+ where +-1+ is the last element.
+ *
+ *     a = [ "a", "b", "c", "d" ]
+ *     a.rotate         #=> ["b", "c", "d", "a"]
+ *     a                #=> ["a", "b", "c", "d"]
+ *     a.rotate(2)      #=> ["c", "d", "a", "b"]
+ *     a.rotate(-3)     #=> ["b", "c", "d", "a"]
+ */
+
+static VALUE
+rb_ary_rotate_m(int argc, VALUE *argv, VALUE ary)
+{
+    VALUE rotated;
+    const VALUE *ptr;
+    long len, cnt = 1;
+
+    switch (argc) {
+      case 1: cnt = NUM2LONG(argv[0]);
+      case 0: break;
+      default: rb_scan_args(argc, argv, "01", NULL);
+    }
+
+    len = RARRAY_LEN(ary);
+    rotated = rb_ary_new2(len);
+    if (len > 0) {
+	cnt = rotate_count(cnt, len);
+	ptr = RARRAY_CONST_PTR(ary);
+	len -= cnt;
+	ary_memcpy(rotated, 0, len, ptr + cnt);
+	ary_memcpy(rotated, len, cnt, ptr);
+    }
+    ARY_SET_LEN(rotated, RARRAY_LEN(ary));
+    return rotated;
+}
+
+struct ary_sort_data {
+    VALUE ary;
+    int opt_methods;
+    int opt_inited;
+};
+
+enum {
+    sort_opt_Fixnum,
+    sort_opt_String,
+    sort_optimizable_count
+};
+
+#define STRING_P(s) (RB_TYPE_P((s), T_STRING) && CLASS_OF(s) == rb_cString)
+
+#define SORT_OPTIMIZABLE_BIT(type) (1U << TOKEN_PASTE(sort_opt_,type))
+#define SORT_OPTIMIZABLE(data, type) \
+    (((data)->opt_inited & SORT_OPTIMIZABLE_BIT(type)) ? \
+     ((data)->opt_methods & SORT_OPTIMIZABLE_BIT(type)) : \
+     (((data)->opt_inited |= SORT_OPTIMIZABLE_BIT(type)), \
+      rb_method_basic_definition_p(TOKEN_PASTE(rb_c,type), id_cmp) && \
+      ((data)->opt_methods |= SORT_OPTIMIZABLE_BIT(type))))
+
+static VALUE
+sort_reentered(VALUE ary)
+{
+    if (RBASIC(ary)->klass) {
+	rb_raise(rb_eRuntimeError, "sort reentered");
+    }
+    return Qnil;
+}
+
+static int
+sort_1(const void *ap, const void *bp, void *dummy)
+{
+    struct ary_sort_data *data = dummy;
+    VALUE retval = sort_reentered(data->ary);
+    VALUE a = *(const VALUE *)ap, b = *(const VALUE *)bp;
+    int n;
+
+    retval = rb_yield_values(2, a, b);
+    n = rb_cmpint(retval, a, b);
+    sort_reentered(data->ary);
+    return n;
+}
+
+static int
+sort_2(const void *ap, const void *bp, void *dummy)
+{
+    struct ary_sort_data *data = dummy;
+    VALUE retval = sort_reentered(data->ary);
+    VALUE a = *(const VALUE *)ap, b = *(const VALUE *)bp;
+    int n;
+
+    if (FIXNUM_P(a) && FIXNUM_P(b) && SORT_OPTIMIZABLE(data, Fixnum)) {
+	if ((long)a > (long)b) return 1;
+	if ((long)a < (long)b) return -1;
+	return 0;
+    }
+    if (STRING_P(a) && STRING_P(b) && SORT_OPTIMIZABLE(data, String)) {
+	return rb_str_cmp(a, b);
+    }
+
+    retval = rb_funcallv(a, id_cmp, 1, &b);
+    n = rb_cmpint(retval, a, b);
+    sort_reentered(data->ary);
+
+    return n;
+}
+
+/*
+ *  call-seq:
+ *     ary.sort!                   -> ary
+ *     ary.sort! { |a, b| block }  -> ary
+ *
+ *  Sorts +self+ in place.
+ *
+ *  Comparisons for the sort will be done using the <code><=></code> operator
+ *  or using an optional code block.
+ *
+ *  The block must implement a comparison between +a+ and +b+, and return
+ *  +-1+, when +a+ follows +b+, +0+ when +a+ and +b+ are equivalent, or ++1+
+ *  if +b+ follows +a+.
+ *
+ *  See also Enumerable#sort_by.
+ *
+ *     a = [ "d", "a", "e", "c", "b" ]
+ *     a.sort!                    #=> ["a", "b", "c", "d", "e"]
+ *     a.sort! { |x,y| y <=> x }  #=> ["e", "d", "c", "b", "a"]
+ */
+
+VALUE
+rb_ary_sort_bang(VALUE ary)
+{
+    rb_ary_modify(ary);
+    assert(!ARY_SHARED_P(ary));
+    if (RARRAY_LEN(ary) > 1) {
+	VALUE tmp = ary_make_substitution(ary); /* only ary refers tmp */
+	struct ary_sort_data data;
+	long len = RARRAY_LEN(ary);
+
+	RBASIC_CLEAR_CLASS(tmp);
+	data.ary = tmp;
+	data.opt_methods = 0;
+	data.opt_inited = 0;
+	RARRAY_PTR_USE(tmp, ptr, {
+	    ruby_qsort(ptr, len, sizeof(VALUE),
+		       rb_block_given_p()?sort_1:sort_2, &data);
+	}); /* WB: no new reference */
+	rb_ary_modify(ary);
+        if (ARY_EMBED_P(tmp)) {
+            if (ARY_SHARED_P(ary)) { /* ary might be destructively operated in the given block */
+                rb_ary_unshare(ary);
+            }
+            FL_SET_EMBED(ary);
+	    ary_memcpy(ary, 0, ARY_EMBED_LEN(tmp), ARY_EMBED_PTR(tmp));
+            ARY_SET_LEN(ary, ARY_EMBED_LEN(tmp));
+        }
+        else {
+            if (!ARY_EMBED_P(ary) && ARY_HEAP_PTR(ary) == ARY_HEAP_PTR(tmp)) {
+                FL_UNSET_SHARED(ary);
+                ARY_SET_CAPA(ary, RARRAY_LEN(tmp));
+            }
+            else {
+                assert(!ARY_SHARED_P(tmp));
+                if (ARY_EMBED_P(ary)) {
+                    FL_UNSET_EMBED(ary);
+                }
+                else if (ARY_SHARED_P(ary)) {
+                    /* ary might be destructively operated in the given block */
+                    rb_ary_unshare(ary);
+                }
+                else {
+		    ruby_sized_xfree((void *)ARY_HEAP_PTR(ary), ARY_HEAP_SIZE(ary));
+                }
+                ARY_SET_PTR(ary, RARRAY_CONST_PTR(tmp));
+                ARY_SET_HEAP_LEN(ary, len);
+                ARY_SET_CAPA(ary, RARRAY_LEN(tmp));
+            }
+            /* tmp was lost ownership for the ptr */
+            FL_UNSET(tmp, FL_FREEZE);
+            FL_SET_EMBED(tmp);
+            ARY_SET_EMBED_LEN(tmp, 0);
+            FL_SET(tmp, FL_FREEZE);
+	}
+        /* tmp will be GC'ed. */
+        RBASIC_SET_CLASS_RAW(tmp, rb_cArray); /* rb_cArray must be marked */
+    }
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.sort                   -> new_ary
+ *     ary.sort { |a, b| block }  -> new_ary
+ *
+ *  Returns a new array created by sorting +self+.
+ *
+ *  Comparisons for the sort will be done using the <code><=></code> operator
+ *  or using an optional code block.
+ *
+ *  The block must implement a comparison between +a+ and +b+, and return
+ *  +-1+, when +a+ follows +b+, +0+ when +a+ and +b+ are equivalent, or ++1+
+ *  if +b+ follows +a+.
+ *
+ *
+ *  See also Enumerable#sort_by.
+ *
+ *     a = [ "d", "a", "e", "c", "b" ]
+ *     a.sort                    #=> ["a", "b", "c", "d", "e"]
+ *     a.sort { |x,y| y <=> x }  #=> ["e", "d", "c", "b", "a"]
+ */
+
+VALUE
+rb_ary_sort(VALUE ary)
+{
+    ary = rb_ary_dup(ary);
+    rb_ary_sort_bang(ary);
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.bsearch {|x| block }  -> elem
+ *
+ *  By using binary search, finds a value from this array which meets
+ *  the given condition in O(log n) where n is the size of the array.
+ *
+ *  You can use this method in two use cases: a find-minimum mode and
+ *  a find-any mode.  In either case, the elements of the array must be
+ *  monotone (or sorted) with respect to the block.
+ *
+ *  In find-minimum mode (this is a good choice for typical use case),
+ *  the block must return true or false, and there must be an index i
+ *  (0 <= i <= ary.size) so that:
+ *
+ *  - the block returns false for any element whose index is less than
+ *    i, and
+ *  - the block returns true for any element whose index is greater
+ *    than or equal to i.
+ *
+ *  This method returns the i-th element.  If i is equal to ary.size,
+ *  it returns nil.
+ *
+ *     ary = [0, 4, 7, 10, 12]
+ *     ary.bsearch {|x| x >=   4 } #=> 4
+ *     ary.bsearch {|x| x >=   6 } #=> 7
+ *     ary.bsearch {|x| x >=  -1 } #=> 0
+ *     ary.bsearch {|x| x >= 100 } #=> nil
+ *
+ *  In find-any mode (this behaves like libc's bsearch(3)), the block
+ *  must return a number, and there must be two indices i and j
+ *  (0 <= i <= j <= ary.size) so that:
+ *
+ *  - the block returns a positive number for ary[k] if 0 <= k < i,
+ *  - the block returns zero for ary[k] if i <= k < j, and
+ *  - the block returns a negative number for ary[k] if
+ *    j <= k < ary.size.
+ *
+ *  Under this condition, this method returns any element whose index
+ *  is within i...j.  If i is equal to j (i.e., there is no element
+ *  that satisfies the block), this method returns nil.
+ *
+ *     ary = [0, 4, 7, 10, 12]
+ *     # try to find v such that 4 <= v < 8
+ *     ary.bsearch {|x| 1 - x / 4 } #=> 4 or 7
+ *     # try to find v such that 8 <= v < 10
+ *     ary.bsearch {|x| 4 - x / 2 } #=> nil
+ *
+ *  You must not mix the two modes at a time; the block must always
+ *  return either true/false, or always return a number.  It is
+ *  undefined which value is actually picked up at each iteration.
+ */
+
+static VALUE
+rb_ary_bsearch(VALUE ary)
+{
+    long low = 0, high = RARRAY_LEN(ary), mid;
+    int smaller = 0, satisfied = 0;
+    VALUE v, val;
+
+    RETURN_ENUMERATOR(ary, 0, 0);
+    while (low < high) {
+	mid = low + ((high - low) / 2);
+	val = rb_ary_entry(ary, mid);
+	v = rb_yield(val);
+	if (FIXNUM_P(v)) {
+	    if (FIX2INT(v) == 0) return val;
+	    smaller = FIX2INT(v) < 0;
+	}
+	else if (v == Qtrue) {
+	    satisfied = 1;
+	    smaller = 1;
+	}
+	else if (v == Qfalse || v == Qnil) {
+	    smaller = 0;
+	}
+	else if (rb_obj_is_kind_of(v, rb_cNumeric)) {
+	    const VALUE zero = INT2FIX(0);
+	    switch (rb_cmpint(rb_funcallv(v, id_cmp, 1, &zero), v, INT2FIX(0))) {
+		case 0: return val;
+		case 1: smaller = 1; break;
+		case -1: smaller = 0;
+	    }
+	}
+	else {
+	    rb_raise(rb_eTypeError, "wrong argument type %s"
+		" (must be numeric, true, false or nil)",
+		rb_obj_classname(v));
+	}
+	if (smaller) {
+	    high = mid;
+	}
+	else {
+	    low = mid + 1;
+	}
+    }
+    if (low == RARRAY_LEN(ary)) return Qnil;
+    if (!satisfied) return Qnil;
+    return rb_ary_entry(ary, low);
+}
+
+
+static VALUE
+sort_by_i(RB_BLOCK_CALL_FUNC_ARGLIST(i, dummy))
+{
+    return rb_yield(i);
+}
+
+/*
+ *  call-seq:
+ *     ary.sort_by! { |obj| block }    -> ary
+ *     ary.sort_by!                    -> Enumerator
+ *
+ *  Sorts +self+ in place using a set of keys generated by mapping the
+ *  values in +self+ through the given block.
+ *
+ *  If no block is given, an Enumerator is returned instead.
+ *
+ */
+
+static VALUE
+rb_ary_sort_by_bang(VALUE ary)
+{
+    VALUE sorted;
+
+    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
+    rb_ary_modify(ary);
+    sorted = rb_block_call(ary, rb_intern("sort_by"), 0, 0, sort_by_i, 0);
+    rb_ary_replace(ary, sorted);
+    return ary;
+}
+
+
+/*
+ *  call-seq:
+ *     ary.collect { |item| block }  -> new_ary
+ *     ary.map     { |item| block }  -> new_ary
+ *     ary.collect                   -> Enumerator
+ *     ary.map                       -> Enumerator
+ *
+ *  Invokes the given block once for each element of +self+.
+ *
+ *  Creates a new array containing the values returned by the block.
+ *
+ *  See also Enumerable#collect.
+ *
+ *  If no block is given, an Enumerator is returned instead.
+ *
+ *     a = [ "a", "b", "c", "d" ]
+ *     a.collect { |x| x + "!" }        #=> ["a!", "b!", "c!", "d!"]
+ *     a.map.with_index{ |x, i| x * i } #=> ["", "b", "cc", "ddd"]
+ *     a                                #=> ["a", "b", "c", "d"]
+ */
+
+static VALUE
+rb_ary_collect(VALUE ary)
+{
+    long i;
+    VALUE collect;
+
+    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
+    collect = rb_ary_new2(RARRAY_LEN(ary));
+    for (i = 0; i < RARRAY_LEN(ary); i++) {
+	rb_ary_push(collect, rb_yield(RARRAY_AREF(ary, i)));
+    }
+    return collect;
+}
+
+
+/*
+ *  call-seq:
+ *     ary.collect! {|item| block }   -> ary
+ *     ary.map!     {|item| block }   -> ary
+ *     ary.collect!                   -> Enumerator
+ *     ary.map!                       -> Enumerator
+ *
+ *  Invokes the given block once for each element of +self+, replacing the
+ *  element with the value returned by the block.
+ *
+ *  See also Enumerable#collect.
+ *
+ *  If no block is given, an Enumerator is returned instead.
+ *
+ *     a = [ "a", "b", "c", "d" ]
+ *     a.map! {|x| x + "!" }
+ *     a #=>  [ "a!", "b!", "c!", "d!" ]
+ *     a.collect!.with_index {|x, i| x[0...i] }
+ *     a #=>  ["", "b", "c!", "d!"]
+ */
+
+static VALUE
+rb_ary_collect_bang(VALUE ary)
+{
+    long i;
+
+    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
+    rb_ary_modify(ary);
+    for (i = 0; i < RARRAY_LEN(ary); i++) {
+	rb_ary_store(ary, i, rb_yield(RARRAY_AREF(ary, i)));
+    }
+    return ary;
+}
+
+VALUE
+rb_get_values_at(VALUE obj, long olen, int argc, const VALUE *argv, VALUE (*func) (VALUE, long))
+{
+    VALUE result = rb_ary_new2(argc);
+    long beg, len, i, j;
+
+    for (i=0; i<argc; i++) {
+	if (FIXNUM_P(argv[i])) {
+	    rb_ary_push(result, (*func)(obj, FIX2LONG(argv[i])));
+	    continue;
+	}
+	/* check if idx is Range */
+	if (rb_range_beg_len(argv[i], &beg, &len, olen, 1)) {
+	    long end = olen < beg+len ? olen : beg+len;
+	    for (j = beg; j < end; j++) {
+		rb_ary_push(result, (*func)(obj, j));
+	    }
+	    if (beg + len > j)
+		rb_ary_resize(result, RARRAY_LEN(result) + (beg + len) - j);
+	    continue;
+	}
+	rb_ary_push(result, (*func)(obj, NUM2LONG(argv[i])));
+    }
+    return result;
+}
+
+/*
+ *  call-seq:
+ *     ary.values_at(selector, ...)  -> new_ary
+ *
+ *  Returns an array containing the elements in +self+ corresponding to the
+ *  given +selector+(s).
+ *
+ *  The selectors may be either integer indices or ranges.
+ *
+ *  See also Array#select.
+ *
+ *     a = %w{ a b c d e f }
+ *     a.values_at(1, 3, 5)          # => ["b", "d", "f"]
+ *     a.values_at(1, 3, 5, 7)       # => ["b", "d", "f", nil]
+ *     a.values_at(-1, -2, -2, -7)   # => ["f", "e", "e", nil]
+ *     a.values_at(4..6, 3...6)      # => ["e", "f", nil, "d", "e", "f"]
+ */
+
+static VALUE
+rb_ary_values_at(int argc, VALUE *argv, VALUE ary)
+{
+    return rb_get_values_at(ary, RARRAY_LEN(ary), argc, argv, rb_ary_entry);
+}
+
+
+/*
+ *  call-seq:
+ *     ary.select { |item| block } -> new_ary
+ *     ary.select                  -> Enumerator
+ *
+ *  Returns a new array containing all elements of +ary+
+ *  for which the given +block+ returns a true value.
+ *
+ *  If no block is given, an Enumerator is returned instead.
+ *
+ *     [1,2,3,4,5].select { |num|  num.even?  }   #=> [2, 4]
+ *
+ *     a = %w{ a b c d e f }
+ *     a.select { |v| v =~ /[aeiou]/ }  #=> ["a", "e"]
+ *
+ *  See also Enumerable#select.
+ */
+
+static VALUE
+rb_ary_select(VALUE ary)
+{
+    VALUE result;
+    long i;
+
+    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
+    result = rb_ary_new2(RARRAY_LEN(ary));
+    for (i = 0; i < RARRAY_LEN(ary); i++) {
+	if (RTEST(rb_yield(RARRAY_AREF(ary, i)))) {
+	    rb_ary_push(result, rb_ary_elt(ary, i));
+	}
+    }
+    return result;
+}
+
+/*
+ *  call-seq:
+ *     ary.select!  {|item| block } -> ary or nil
+ *     ary.select!                  -> Enumerator
+ *
+ *  Invokes the given block passing in successive elements from +self+,
+ *  deleting elements for which the block returns a +false+ value.
+ *
+ *  If changes were made, it will return +self+, otherwise it returns +nil+.
+ *
+ *  See also Array#keep_if
+ *
+ *  If no block is given, an Enumerator is returned instead.
+ *
+ */
+
+static VALUE
+rb_ary_select_bang(VALUE ary)
+{
+    long i1, i2;
+
+    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
+    rb_ary_modify(ary);
+    for (i1 = i2 = 0; i1 < RARRAY_LEN(ary); i1++) {
+	VALUE v = RARRAY_AREF(ary, i1);
+	if (!RTEST(rb_yield(v))) continue;
+	if (i1 != i2) {
+	    rb_ary_store(ary, i2, v);
+	}
+	i2++;
+    }
+
+    if (i1 == i2) return Qnil;
+    if (i2 < i1)
+	ARY_SET_LEN(ary, i2);
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.keep_if { |item| block } -> ary
+ *     ary.keep_if                  -> Enumerator
+ *
+ *  Deletes every element of +self+ for which the given block evaluates to
+ *  +false+.
+ *
+ *  See also Array#select!
+ *
+ *  If no block is given, an Enumerator is returned instead.
+ *
+ *     a = %w{ a b c d e f }
+ *     a.keep_if { |v| v =~ /[aeiou]/ }  #=> ["a", "e"]
+ */
+
+static VALUE
+rb_ary_keep_if(VALUE ary)
+{
+    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
+    rb_ary_select_bang(ary);
+    return ary;
+}
+
+static void
+ary_resize_smaller(VALUE ary, long len)
+{
+    rb_ary_modify(ary);
+    if (RARRAY_LEN(ary) > len) {
+	ARY_SET_LEN(ary, len);
+	if (len * 2 < ARY_CAPA(ary) &&
+	    ARY_CAPA(ary) > ARY_DEFAULT_SIZE) {
+	    ary_resize_capa(ary, len * 2);
+	}
+    }
+}
+
+/*
+ *  call-seq:
+ *     ary.delete(obj)            -> item or nil
+ *     ary.delete(obj) { block }  -> item or result of block
+ *
+ *  Deletes all items from +self+ that are equal to +obj+.
+ *
+ *  Returns the last deleted item, or +nil+ if no matching item is found.
+ *
+ *  If the optional code block is given, the result of the block is returned if
+ *  the item is not found.  (To remove +nil+ elements and get an informative
+ *  return value, use Array#compact!)
+ *
+ *     a = [ "a", "b", "b", "b", "c" ]
+ *     a.delete("b")                   #=> "b"
+ *     a                               #=> ["a", "c"]
+ *     a.delete("z")                   #=> nil
+ *     a.delete("z") { "not found" }   #=> "not found"
+ */
+
+VALUE
+rb_ary_delete(VALUE ary, VALUE item)
+{
+    VALUE v = item;
+    long i1, i2;
+
+    for (i1 = i2 = 0; i1 < RARRAY_LEN(ary); i1++) {
+	VALUE e = RARRAY_AREF(ary, i1);
+
+	if (rb_equal(e, item)) {
+	    v = e;
+	    continue;
+	}
+	if (i1 != i2) {
+	    rb_ary_store(ary, i2, e);
+	}
+	i2++;
+    }
+    if (RARRAY_LEN(ary) == i2) {
+	if (rb_block_given_p()) {
+	    return rb_yield(item);
+	}
+	return Qnil;
+    }
+
+    ary_resize_smaller(ary, i2);
+
+    return v;
+}
+
+void
+rb_ary_delete_same(VALUE ary, VALUE item)
+{
+    long i1, i2;
+
+    for (i1 = i2 = 0; i1 < RARRAY_LEN(ary); i1++) {
+	VALUE e = RARRAY_AREF(ary, i1);
+
+	if (e == item) {
+	    continue;
+	}
+	if (i1 != i2) {
+	    rb_ary_store(ary, i2, e);
+	}
+	i2++;
+    }
+    if (RARRAY_LEN(ary) == i2) {
+	return;
+    }
+
+    ary_resize_smaller(ary, i2);
+}
+
+VALUE
+rb_ary_delete_at(VALUE ary, long pos)
+{
+    long len = RARRAY_LEN(ary);
+    VALUE del;
+
+    if (pos >= len) return Qnil;
+    if (pos < 0) {
+	pos += len;
+	if (pos < 0) return Qnil;
+    }
+
+    rb_ary_modify(ary);
+    del = RARRAY_AREF(ary, pos);
+    RARRAY_PTR_USE(ary, ptr, {
+	MEMMOVE(ptr+pos, ptr+pos+1, VALUE, len-pos-1);
+    });
+    ARY_INCREASE_LEN(ary, -1);
+
+    return del;
+}
+
+/*
+ *  call-seq:
+ *     ary.delete_at(index)  -> obj or nil
+ *
+ *  Deletes the element at the specified +index+, returning that element, or
+ *  +nil+ if the +index+ is out of range.
+ *
+ *  See also Array#slice!
+ *
+ *     a = ["ant", "bat", "cat", "dog"]
+ *     a.delete_at(2)    #=> "cat"
+ *     a                 #=> ["ant", "bat", "dog"]
+ *     a.delete_at(99)   #=> nil
+ */
+
+static VALUE
+rb_ary_delete_at_m(VALUE ary, VALUE pos)
+{
+    return rb_ary_delete_at(ary, NUM2LONG(pos));
+}
+
+/*
+ *  call-seq:
+ *     ary.slice!(index)         -> obj or nil
+ *     ary.slice!(start, length) -> new_ary or nil
+ *     ary.slice!(range)         -> new_ary or nil
+ *
+ *  Deletes the element(s) given by an +index+ (optionally up to +length+
+ *  elements) or by a +range+.
+ *
+ *  Returns the deleted object (or objects), or +nil+ if the +index+ is out of
+ *  range.
+ *
+ *     a = [ "a", "b", "c" ]
+ *     a.slice!(1)     #=> "b"
+ *     a               #=> ["a", "c"]
+ *     a.slice!(-1)    #=> "c"
+ *     a               #=> ["a"]
+ *     a.slice!(100)   #=> nil
+ *     a               #=> ["a"]
+ */
+
+static VALUE
+rb_ary_slice_bang(int argc, VALUE *argv, VALUE ary)
+{
+    VALUE arg1, arg2;
+    long pos, len, orig_len;
+
+    rb_ary_modify_check(ary);
+    if (argc == 2) {
+	pos = NUM2LONG(argv[0]);
+	len = NUM2LONG(argv[1]);
+      delete_pos_len:
+	if (len < 0) return Qnil;
+	orig_len = RARRAY_LEN(ary);
+	if (pos < 0) {
+	    pos += orig_len;
+	    if (pos < 0) return Qnil;
+	}
+	else if (orig_len < pos) return Qnil;
+	if (orig_len < pos + len) {
+	    len = orig_len - pos;
+	}
+	if (len == 0) return rb_ary_new2(0);
+	arg2 = rb_ary_new4(len, RARRAY_CONST_PTR(ary)+pos);
+	RBASIC_SET_CLASS(arg2, rb_obj_class(ary));
+	rb_ary_splice(ary, pos, len, Qundef);
+	return arg2;
+    }
+
+    if (argc != 1) {
+	/* error report */
+	rb_scan_args(argc, argv, "11", NULL, NULL);
+    }
+    arg1 = argv[0];
+
+    if (!FIXNUM_P(arg1)) {
+	switch (rb_range_beg_len(arg1, &pos, &len, RARRAY_LEN(ary), 0)) {
+	  case Qtrue:
+	    /* valid range */
+	    goto delete_pos_len;
+	  case Qnil:
+	    /* invalid range */
+	    return Qnil;
+	  default:
+	    /* not a range */
+	    break;
+	}
+    }
+
+    return rb_ary_delete_at(ary, NUM2LONG(arg1));
+}
+
+static VALUE
+ary_reject(VALUE orig, VALUE result)
+{
+    long i;
+
+    for (i = 0; i < RARRAY_LEN(orig); i++) {
+	VALUE v = RARRAY_AREF(orig, i);
+	if (!RTEST(rb_yield(v))) {
+	    rb_ary_push(result, v);
+	}
+    }
+    return result;
+}
+
+static VALUE
+ary_reject_bang(VALUE ary)
+{
+    long i;
+    VALUE result = Qnil;
+
+    rb_ary_modify_check(ary);
+    for (i = 0; i < RARRAY_LEN(ary); ) {
+	VALUE v = RARRAY_AREF(ary, i);
+	if (RTEST(rb_yield(v))) {
+	    rb_ary_delete_at(ary, i);
+	    result = ary;
+	}
+	else {
+	    i++;
+	}
+    }
+    return result;
+}
+
+/*
+ *  call-seq:
+ *     ary.reject! { |item| block }  -> ary or nil
+ *     ary.reject!                   -> Enumerator
+ *
+ *  Equivalent to Array#delete_if, deleting elements from +self+ for which the
+ *  block evaluates to +true+, but returns +nil+ if no changes were made.
+ *
+ *  The array is changed instantly every time the block is called, not after
+ *  the iteration is over.
+ *
+ *  See also Enumerable#reject and Array#delete_if.
+ *
+ *  If no block is given, an Enumerator is returned instead.
+ */
+
+static VALUE
+rb_ary_reject_bang(VALUE ary)
+{
+    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
+    return ary_reject_bang(ary);
+}
+
+/*
+ *  call-seq:
+ *     ary.reject  {|item| block }  -> new_ary
+ *     ary.reject                   -> Enumerator
+ *
+ *  Returns a new array containing the items in +self+ for which the given
+ *  block is not +true+.
+ *
+ *  See also Array#delete_if
+ *
+ *  If no block is given, an Enumerator is returned instead.
+ */
+
+static VALUE
+rb_ary_reject(VALUE ary)
+{
+    VALUE rejected_ary;
+
+    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
+    rejected_ary = rb_ary_new();
+    ary_reject(ary, rejected_ary);
+    return rejected_ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.delete_if { |item| block }  -> ary
+ *     ary.delete_if                   -> Enumerator
+ *
+ *  Deletes every element of +self+ for which block evaluates to +true+.
+ *
+ *  The array is changed instantly every time the block is called, not after
+ *  the iteration is over.
+ *
+ *  See also Array#reject!
+ *
+ *  If no block is given, an Enumerator is returned instead.
+ *
+ *     scores = [ 97, 42, 75 ]
+ *     scores.delete_if {|score| score < 80 }   #=> [97]
+ */
+
+static VALUE
+rb_ary_delete_if(VALUE ary)
+{
+    RETURN_SIZED_ENUMERATOR(ary, 0, 0, ary_enum_length);
+    ary_reject_bang(ary);
+    return ary;
+}
+
+static VALUE
+take_i(RB_BLOCK_CALL_FUNC_ARGLIST(val, cbarg))
+{
+    VALUE *args = (VALUE *)cbarg;
+    if (args[1]-- == 0) rb_iter_break();
+    if (argc > 1) val = rb_ary_new4(argc, argv);
+    rb_ary_push(args[0], val);
+    return Qnil;
+}
+
+static VALUE
+take_items(VALUE obj, long n)
+{
+    VALUE result = rb_check_array_type(obj);
+    VALUE args[2];
+
+    if (!NIL_P(result)) return rb_ary_subseq(result, 0, n);
+    result = rb_ary_new2(n);
+    args[0] = result; args[1] = (VALUE)n;
+    if (rb_check_block_call(obj, idEach, 0, 0, take_i, (VALUE)args) == Qundef)
+	rb_raise(rb_eTypeError, "wrong argument type %"PRIsVALUE" (must respond to :each)",
+		 rb_obj_class(obj));
+    return result;
+}
+
+
+/*
+ *  call-seq:
+ *     ary.zip(arg, ...)                  -> new_ary
+ *     ary.zip(arg, ...) { |arr| block }  -> nil
+ *
+ *  Converts any arguments to arrays, then merges elements of +self+ with
+ *  corresponding elements from each argument.
+ *
+ *  This generates a sequence of <code>ary.size</code> _n_-element arrays,
+ *  where _n_ is one more than the count of arguments.
+ *
+ *  If the size of any argument is less than the size of the initial array,
+ *  +nil+ values are supplied.
+ *
+ *  If a block is given, it is invoked for each output +array+, otherwise an
+ *  array of arrays is returned.
+ *
+ *     a = [ 4, 5, 6 ]
+ *     b = [ 7, 8, 9 ]
+ *     [1, 2, 3].zip(a, b)   #=> [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
+ *     [1, 2].zip(a, b)      #=> [[1, 4, 7], [2, 5, 8]]
+ *     a.zip([1, 2], [8])    #=> [[4, 1, 8], [5, 2, nil], [6, nil, nil]]
+ */
+
+static VALUE
+rb_ary_zip(int argc, VALUE *argv, VALUE ary)
+{
+    int i, j;
+    long len = RARRAY_LEN(ary);
+    VALUE result = Qnil;
+
+    for (i=0; i<argc; i++) {
+	argv[i] = take_items(argv[i], len);
+    }
+
+    if (rb_block_given_p()) {
+	int arity = rb_block_arity();
+
+	if (arity > 1) {
+	    VALUE work, *tmp;
+
+	    tmp = ALLOCV_N(VALUE, work, argc+1);
+
+	    for (i=0; i<RARRAY_LEN(ary); i++) {
+		tmp[0] = RARRAY_AREF(ary, i);
+		for (j=0; j<argc; j++) {
+		    tmp[j+1] = rb_ary_elt(argv[j], i);
+		}
+		rb_yield_values2(argc+1, tmp);
+	    }
+
+	    if (work) ALLOCV_END(work);
+	}
+	else {
+	    for (i=0; i<RARRAY_LEN(ary); i++) {
+		VALUE tmp = rb_ary_new2(argc+1);
+
+		rb_ary_push(tmp, RARRAY_AREF(ary, i));
+		for (j=0; j<argc; j++) {
+		    rb_ary_push(tmp, rb_ary_elt(argv[j], i));
+		}
+		rb_yield(tmp);
+	    }
+	}
+    }
+    else {
+	result = rb_ary_new_capa(len);
+
+	for (i=0; i<len; i++) {
+	    VALUE tmp = rb_ary_new_capa(argc+1);
+
+	    rb_ary_push(tmp, RARRAY_AREF(ary, i));
+	    for (j=0; j<argc; j++) {
+		rb_ary_push(tmp, rb_ary_elt(argv[j], i));
+	    }
+	    rb_ary_push(result, tmp);
+	}
+    }
+
+    return result;
+}
+
+/*
+ *  call-seq:
+ *     ary.transpose -> new_ary
+ *
+ *  Assumes that +self+ is an array of arrays and transposes the rows and
+ *  columns.
+ *
+ *     a = [[1,2], [3,4], [5,6]]
+ *     a.transpose   #=> [[1, 3, 5], [2, 4, 6]]
+ *
+ *  If the length of the subarrays don't match, an IndexError is raised.
+ */
+
+static VALUE
+rb_ary_transpose(VALUE ary)
+{
+    long elen = -1, alen, i, j;
+    VALUE tmp, result = 0;
+
+    alen = RARRAY_LEN(ary);
+    if (alen == 0) return rb_ary_dup(ary);
+    for (i=0; i<alen; i++) {
+	tmp = to_ary(rb_ary_elt(ary, i));
+	if (elen < 0) {		/* first element */
+	    elen = RARRAY_LEN(tmp);
+	    result = rb_ary_new2(elen);
+	    for (j=0; j<elen; j++) {
+		rb_ary_store(result, j, rb_ary_new2(alen));
+	    }
+	}
+	else if (elen != RARRAY_LEN(tmp)) {
+	    rb_raise(rb_eIndexError, "element size differs (%ld should be %ld)",
+		     RARRAY_LEN(tmp), elen);
+	}
+	for (j=0; j<elen; j++) {
+	    rb_ary_store(rb_ary_elt(result, j), i, rb_ary_elt(tmp, j));
+	}
+    }
+    return result;
+}
+
+/*
+ *  call-seq:
+ *     ary.replace(other_ary)  -> ary
+ *     ary.initialize_copy(other_ary)	-> ary
+ *
+ *  Replaces the contents of +self+ with the contents of +other_ary+,
+ *  truncating or expanding if necessary.
+ *
+ *     a = [ "a", "b", "c", "d", "e" ]
+ *     a.replace([ "x", "y", "z" ])   #=> ["x", "y", "z"]
+ *     a                              #=> ["x", "y", "z"]
+ */
+
+VALUE
+rb_ary_replace(VALUE copy, VALUE orig)
+{
+    rb_ary_modify_check(copy);
+    orig = to_ary(orig);
+    if (copy == orig) return copy;
+
+    if (RARRAY_LEN(orig) <= RARRAY_EMBED_LEN_MAX) {
+        VALUE shared = 0;
+
+        if (ARY_OWNS_HEAP_P(copy)) {
+	    RARRAY_PTR_USE(copy, ptr, ruby_sized_xfree(ptr, ARY_HEAP_SIZE(copy)));
+	}
+        else if (ARY_SHARED_P(copy)) {
+            shared = ARY_SHARED(copy);
+            FL_UNSET_SHARED(copy);
+        }
+        FL_SET_EMBED(copy);
+	ary_memcpy(copy, 0, RARRAY_LEN(orig), RARRAY_CONST_PTR(orig));
+        if (shared) {
+            rb_ary_decrement_share(shared);
+        }
+        ARY_SET_LEN(copy, RARRAY_LEN(orig));
+    }
+    else {
+        VALUE shared = ary_make_shared(orig);
+        if (ARY_OWNS_HEAP_P(copy)) {
+	    RARRAY_PTR_USE(copy, ptr, ruby_sized_xfree(ptr, ARY_HEAP_SIZE(copy)));
+        }
+        else {
+            rb_ary_unshare_safe(copy);
+        }
+        FL_UNSET_EMBED(copy);
+        ARY_SET_PTR(copy, RARRAY_CONST_PTR(orig));
+        ARY_SET_LEN(copy, RARRAY_LEN(orig));
+        rb_ary_set_shared(copy, shared);
+    }
+    return copy;
+}
+
+/*
+ *  call-seq:
+ *     ary.clear    -> ary
+ *
+ *  Removes all elements from +self+.
+ *
+ *     a = [ "a", "b", "c", "d", "e" ]
+ *     a.clear    #=> [ ]
+ */
+
+VALUE
+rb_ary_clear(VALUE ary)
+{
+    rb_ary_modify_check(ary);
+    ARY_SET_LEN(ary, 0);
+    if (ARY_SHARED_P(ary)) {
+	if (!ARY_EMBED_P(ary)) {
+	    rb_ary_unshare(ary);
+	    FL_SET_EMBED(ary);
+	}
+    }
+    else if (ARY_DEFAULT_SIZE * 2 < ARY_CAPA(ary)) {
+	ary_resize_capa(ary, ARY_DEFAULT_SIZE * 2);
+    }
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.fill(obj)                                 -> ary
+ *     ary.fill(obj, start [, length])               -> ary
+ *     ary.fill(obj, range )                         -> ary
+ *     ary.fill { |index| block }                    -> ary
+ *     ary.fill(start [, length] ) { |index| block } -> ary
+ *     ary.fill(range) { |index| block }             -> ary
+ *
+ *  The first three forms set the selected elements of +self+ (which
+ *  may be the entire array) to +obj+.
+ *
+ *  A +start+ of +nil+ is equivalent to zero.
+ *
+ *  A +length+ of +nil+ is equivalent to the length of the array.
+ *
+ *  The last three forms fill the array with the value of the given block,
+ *  which is passed the absolute index of each element to be filled.
+ *
+ *  Negative values of +start+ count from the end of the array, where +-1+ is
+ *  the last element.
+ *
+ *     a = [ "a", "b", "c", "d" ]
+ *     a.fill("x")              #=> ["x", "x", "x", "x"]
+ *     a.fill("z", 2, 2)        #=> ["x", "x", "z", "z"]
+ *     a.fill("y", 0..1)        #=> ["y", "y", "z", "z"]
+ *     a.fill { |i| i*i }       #=> [0, 1, 4, 9]
+ *     a.fill(-2) { |i| i*i*i } #=> [0, 1, 8, 27]
+ */
+
+static VALUE
+rb_ary_fill(int argc, VALUE *argv, VALUE ary)
+{
+    VALUE item, arg1, arg2;
+    long beg = 0, end = 0, len = 0;
+    int block_p = FALSE;
+
+    if (rb_block_given_p()) {
+	block_p = TRUE;
+	rb_scan_args(argc, argv, "02", &arg1, &arg2);
+	argc += 1;		/* hackish */
+    }
+    else {
+	rb_scan_args(argc, argv, "12", &item, &arg1, &arg2);
+    }
+    switch (argc) {
+      case 1:
+	beg = 0;
+	len = RARRAY_LEN(ary);
+	break;
+      case 2:
+	if (rb_range_beg_len(arg1, &beg, &len, RARRAY_LEN(ary), 1)) {
+	    break;
+	}
+	/* fall through */
+      case 3:
+	beg = NIL_P(arg1) ? 0 : NUM2LONG(arg1);
+	if (beg < 0) {
+	    beg = RARRAY_LEN(ary) + beg;
+	    if (beg < 0) beg = 0;
+	}
+	len = NIL_P(arg2) ? RARRAY_LEN(ary) - beg : NUM2LONG(arg2);
+	break;
+    }
+    rb_ary_modify(ary);
+    if (len < 0) {
+        return ary;
+    }
+    if (beg >= ARY_MAX_SIZE || len > ARY_MAX_SIZE - beg) {
+	rb_raise(rb_eArgError, "argument too big");
+    }
+    end = beg + len;
+    if (RARRAY_LEN(ary) < end) {
+	if (end >= ARY_CAPA(ary)) {
+	    ary_resize_capa(ary, end);
+	}
+	ary_mem_clear(ary, RARRAY_LEN(ary), end - RARRAY_LEN(ary));
+	ARY_SET_LEN(ary, end);
+    }
+
+    if (block_p) {
+	VALUE v;
+	long i;
+
+	for (i=beg; i<end; i++) {
+	    v = rb_yield(LONG2NUM(i));
+	    if (i>=RARRAY_LEN(ary)) break;
+	    ARY_SET(ary, i, v);
+	}
+    }
+    else {
+	ary_memfill(ary, beg, len, item);
+    }
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary + other_ary   -> new_ary
+ *
+ *  Concatenation --- Returns a new array built by concatenating the
+ *  two arrays together to produce a third array.
+ *
+ *     [ 1, 2, 3 ] + [ 4, 5 ]    #=> [ 1, 2, 3, 4, 5 ]
+ *     a = [ "a", "b", "c" ]
+ *     c = a + [ "d", "e", "f" ]
+ *     c                         #=> [ "a", "b", "c", "d", "e", "f" ]
+ *     a                         #=> [ "a", "b", "c" ]
+ *
+ *  Note that
+ *     x += y
+ *  is the same as
+ *     x = x + y
+ *  This means that it produces a new array. As a consequence,
+ *  repeated use of <code>+=</code> on arrays can be quite inefficient.
+ *
+ *  See also Array#concat.
+ */
+
+VALUE
+rb_ary_plus(VALUE x, VALUE y)
+{
+    VALUE z;
+    long len, xlen, ylen;
+
+    y = to_ary(y);
+    xlen = RARRAY_LEN(x);
+    ylen = RARRAY_LEN(y);
+    len = xlen + ylen;
+    z = rb_ary_new2(len);
+
+    ary_memcpy(z, 0, xlen, RARRAY_CONST_PTR(x));
+    ary_memcpy(z, xlen, ylen, RARRAY_CONST_PTR(y));
+    ARY_SET_LEN(z, len);
+    return z;
+}
+
+/*
+ *  call-seq:
+ *     ary.concat(other_ary)   -> ary
+ *
+ *  Appends the elements of +other_ary+ to +self+.
+ *
+ *     [ "a", "b" ].concat( ["c", "d"] ) #=> [ "a", "b", "c", "d" ]
+ *     a = [ 1, 2, 3 ]
+ *     a.concat( [ 4, 5 ] )
+ *     a                                 #=> [ 1, 2, 3, 4, 5 ]
+ *
+ *  See also Array#+.
+ */
+
+VALUE
+rb_ary_concat(VALUE x, VALUE y)
+{
+    rb_ary_modify_check(x);
+    y = to_ary(y);
+    if (RARRAY_LEN(y) > 0) {
+	rb_ary_splice(x, RARRAY_LEN(x), 0, y);
+    }
+    return x;
+}
+
+
+/*
+ *  call-seq:
+ *     ary * int     -> new_ary
+ *     ary * str     -> new_string
+ *
+ *  Repetition --- With a String argument, equivalent to
+ *  <code>ary.join(str)</code>.
+ *
+ *  Otherwise, returns a new array built by concatenating the +int+ copies of
+ *  +self+.
+ *
+ *
+ *     [ 1, 2, 3 ] * 3    #=> [ 1, 2, 3, 1, 2, 3, 1, 2, 3 ]
+ *     [ 1, 2, 3 ] * ","  #=> "1,2,3"
+ *
+ */
+
+static VALUE
+rb_ary_times(VALUE ary, VALUE times)
+{
+    VALUE ary2, tmp;
+    const VALUE *ptr;
+    long t, len;
+
+    tmp = rb_check_string_type(times);
+    if (!NIL_P(tmp)) {
+	return rb_ary_join(ary, tmp);
+    }
+
+    len = NUM2LONG(times);
+    if (len == 0) {
+	ary2 = ary_new(rb_obj_class(ary), 0);
+	goto out;
+    }
+    if (len < 0) {
+	rb_raise(rb_eArgError, "negative argument");
+    }
+    if (ARY_MAX_SIZE/len < RARRAY_LEN(ary)) {
+	rb_raise(rb_eArgError, "argument too big");
+    }
+    len *= RARRAY_LEN(ary);
+
+    ary2 = ary_new(rb_obj_class(ary), len);
+    ARY_SET_LEN(ary2, len);
+
+    ptr = RARRAY_CONST_PTR(ary);
+    t = RARRAY_LEN(ary);
+    if (0 < t) {
+	ary_memcpy(ary2, 0, t, ptr);
+	while (t <= len/2) {
+	    ary_memcpy(ary2, t, t, RARRAY_CONST_PTR(ary2));
+            t *= 2;
+        }
+        if (t < len) {
+	    ary_memcpy(ary2, t, len-t, RARRAY_CONST_PTR(ary2));
+        }
+    }
+  out:
+    OBJ_INFECT(ary2, ary);
+
+    return ary2;
+}
+
+/*
+ *  call-seq:
+ *     ary.assoc(obj)   -> new_ary  or  nil
+ *
+ *  Searches through an array whose elements are also arrays comparing +obj+
+ *  with the first element of each contained array using <code>obj.==</code>.
+ *
+ *  Returns the first contained array that matches (that is, the first
+ *  associated array), or +nil+ if no match is found.
+ *
+ *  See also Array#rassoc
+ *
+ *     s1 = [ "colors", "red", "blue", "green" ]
+ *     s2 = [ "letters", "a", "b", "c" ]
+ *     s3 = "foo"
+ *     a  = [ s1, s2, s3 ]
+ *     a.assoc("letters")  #=> [ "letters", "a", "b", "c" ]
+ *     a.assoc("foo")      #=> nil
+ */
+
+VALUE
+rb_ary_assoc(VALUE ary, VALUE key)
+{
+    long i;
+    VALUE v;
+
+    for (i = 0; i < RARRAY_LEN(ary); ++i) {
+	v = rb_check_array_type(RARRAY_AREF(ary, i));
+	if (!NIL_P(v) && RARRAY_LEN(v) > 0 &&
+	    rb_equal(RARRAY_AREF(v, 0), key))
+	    return v;
+    }
+    return Qnil;
+}
+
+/*
+ *  call-seq:
+ *     ary.rassoc(obj) -> new_ary or nil
+ *
+ *  Searches through the array whose elements are also arrays.
+ *
+ *  Compares +obj+ with the second element of each contained array using
+ *  <code>obj.==</code>.
+ *
+ *  Returns the first contained array that matches +obj+.
+ *
+ *  See also Array#assoc.
+ *
+ *     a = [ [ 1, "one"], [2, "two"], [3, "three"], ["ii", "two"] ]
+ *     a.rassoc("two")    #=> [2, "two"]
+ *     a.rassoc("four")   #=> nil
+ */
+
+VALUE
+rb_ary_rassoc(VALUE ary, VALUE value)
+{
+    long i;
+    VALUE v;
+
+    for (i = 0; i < RARRAY_LEN(ary); ++i) {
+	v = RARRAY_AREF(ary, i);
+	if (RB_TYPE_P(v, T_ARRAY) &&
+	    RARRAY_LEN(v) > 1 &&
+	    rb_equal(RARRAY_AREF(v, 1), value))
+	    return v;
+    }
+    return Qnil;
+}
+
+static VALUE
+recursive_equal(VALUE ary1, VALUE ary2, int recur)
+{
+    long i, len1;
+    const VALUE *p1, *p2;
+
+    if (recur) return Qtrue; /* Subtle! */
+
+    p1 = RARRAY_CONST_PTR(ary1);
+    p2 = RARRAY_CONST_PTR(ary2);
+    len1 = RARRAY_LEN(ary1);
+
+    for (i = 0; i < len1; i++) {
+	if (*p1 != *p2) {
+	    if (rb_equal(*p1, *p2)) {
+		len1 = RARRAY_LEN(ary1);
+		if (len1 != RARRAY_LEN(ary2))
+		    return Qfalse;
+		if (len1 < i)
+		    return Qtrue;
+		p1 = RARRAY_CONST_PTR(ary1) + i;
+		p2 = RARRAY_CONST_PTR(ary2) + i;
+	    }
+	    else {
+		return Qfalse;
+	    }
+	}
+	p1++;
+	p2++;
+    }
+    return Qtrue;
+}
+
+/*
+ *  call-seq:
+ *     ary == other_ary   ->   bool
+ *
+ *  Equality --- Two arrays are equal if they contain the same number of
+ *  elements and if each element is equal to (according to Object#==) the
+ *  corresponding element in +other_ary+.
+ *
+ *     [ "a", "c" ]    == [ "a", "c", 7 ]     #=> false
+ *     [ "a", "c", 7 ] == [ "a", "c", 7 ]     #=> true
+ *     [ "a", "c", 7 ] == [ "a", "d", "f" ]   #=> false
+ *
+ */
+
+static VALUE
+rb_ary_equal(VALUE ary1, VALUE ary2)
+{
+    if (ary1 == ary2) return Qtrue;
+    if (!RB_TYPE_P(ary2, T_ARRAY)) {
+	if (!rb_respond_to(ary2, idTo_ary)) {
+	    return Qfalse;
+	}
+	return rb_equal(ary2, ary1);
+    }
+    if (RARRAY_LEN(ary1) != RARRAY_LEN(ary2)) return Qfalse;
+    if (RARRAY_CONST_PTR(ary1) == RARRAY_CONST_PTR(ary2)) return Qtrue;
+    return rb_exec_recursive_paired(recursive_equal, ary1, ary2, ary2);
+}
+
+static VALUE
+recursive_eql(VALUE ary1, VALUE ary2, int recur)
+{
+    long i;
+
+    if (recur) return Qtrue; /* Subtle! */
+    for (i=0; i<RARRAY_LEN(ary1); i++) {
+	if (!rb_eql(rb_ary_elt(ary1, i), rb_ary_elt(ary2, i)))
+	    return Qfalse;
+    }
+    return Qtrue;
+}
+
+/*
+ *  call-seq:
+ *     ary.eql?(other)  -> true or false
+ *
+ *  Returns +true+ if +self+ and +other+ are the same object,
+ *  or are both arrays with the same content (according to Object#eql?).
+ */
+
+static VALUE
+rb_ary_eql(VALUE ary1, VALUE ary2)
+{
+    if (ary1 == ary2) return Qtrue;
+    if (!RB_TYPE_P(ary2, T_ARRAY)) return Qfalse;
+    if (RARRAY_LEN(ary1) != RARRAY_LEN(ary2)) return Qfalse;
+    if (RARRAY_CONST_PTR(ary1) == RARRAY_CONST_PTR(ary2)) return Qtrue;
+    return rb_exec_recursive_paired(recursive_eql, ary1, ary2, ary2);
+}
+
+/*
+ *  call-seq:
+ *     ary.hash   -> fixnum
+ *
+ *  Compute a hash-code for this array.
+ *
+ *  Two arrays with the same content will have the same hash code (and will
+ *  compare using #eql?).
+ *
+ *  See also Object#hash.
+ */
+
+static VALUE
+rb_ary_hash(VALUE ary)
+{
+    long i;
+    st_index_t h;
+    VALUE n;
+
+    h = rb_hash_start(RARRAY_LEN(ary));
+    h = rb_hash_uint(h, (st_index_t)rb_ary_hash);
+    for (i=0; i<RARRAY_LEN(ary); i++) {
+	n = rb_hash(RARRAY_AREF(ary, i));
+	h = rb_hash_uint(h, NUM2LONG(n));
+    }
+    h = rb_hash_end(h);
+    return LONG2FIX(h);
+}
+
+/*
+ *  call-seq:
+ *     ary.include?(object)   -> true or false
+ *
+ *  Returns +true+ if the given +object+ is present in +self+ (that is, if any
+ *  element <code>==</code> +object+), otherwise returns +false+.
+ *
+ *     a = [ "a", "b", "c" ]
+ *     a.include?("b")   #=> true
+ *     a.include?("z")   #=> false
+ */
+
+VALUE
+rb_ary_includes(VALUE ary, VALUE item)
+{
+    long i;
+    VALUE e;
+
+    for (i=0; i<RARRAY_LEN(ary); i++) {
+	e = RARRAY_AREF(ary, i);
+	switch (rb_equal_opt(e, item)) {
+	  case Qundef:
+	    if (rb_equal(e, item)) return Qtrue;
+	    break;
+	  case Qtrue:
+	    return Qtrue;
+	}
+    }
+    return Qfalse;
+}
+
+
+static VALUE
+recursive_cmp(VALUE ary1, VALUE ary2, int recur)
+{
+    long i, len;
+
+    if (recur) return Qundef;	/* Subtle! */
+    len = RARRAY_LEN(ary1);
+    if (len > RARRAY_LEN(ary2)) {
+	len = RARRAY_LEN(ary2);
+    }
+    for (i=0; i<len; i++) {
+	VALUE e1 = rb_ary_elt(ary1, i), e2 = rb_ary_elt(ary2, i);
+	VALUE v = rb_funcallv(e1, id_cmp, 1, &e2);
+	if (v != INT2FIX(0)) {
+	    return v;
+	}
+    }
+    return Qundef;
+}
+
+/*
+ *  call-seq:
+ *     ary <=> other_ary   ->  -1, 0, +1 or nil
+ *
+ *  Comparison --- Returns an integer (+-1+, +0+, or <code>+1</code>) if this
+ *  array is less than, equal to, or greater than +other_ary+.
+ *
+ *  Each object in each array is compared (using the <=> operator).
+ *
+ *  Arrays are compared in an "element-wise" manner; the first element of +ary+
+ *  is compared with the first one of +other_ary+ using the <=> operator, then
+ *  each of the second elements, etc...
+ *  As soon as the result of any such comparison is non zero (i.e. the two
+ *  corresponding elements are not equal), that result is returned for the
+ *  whole array comparison.
+ *
+ *  If all the elements are equal, then the result is based on a comparison of
+ *  the array lengths. Thus, two arrays are "equal" according to Array#<=> if,
+ *  and only if, they have the same length and the value of each element is
+ *  equal to the value of the corresponding element in the other array.
+ *
+ *  +nil+ is returned if the +other_ary+ is not an array or if the comparison
+ *  of two elements returned +nil+.
+ *
+ *     [ "a", "a", "c" ]    <=> [ "a", "b", "c" ]   #=> -1
+ *     [ 1, 2, 3, 4, 5, 6 ] <=> [ 1, 2 ]            #=> +1
+ *     [ 1, 2 ]             <=> [ 1, :two ]         #=> nil
+ *
+ */
+
+VALUE
+rb_ary_cmp(VALUE ary1, VALUE ary2)
+{
+    long len;
+    VALUE v;
+
+    ary2 = rb_check_array_type(ary2);
+    if (NIL_P(ary2)) return Qnil;
+    if (ary1 == ary2) return INT2FIX(0);
+    v = rb_exec_recursive_paired(recursive_cmp, ary1, ary2, ary2);
+    if (v != Qundef) return v;
+    len = RARRAY_LEN(ary1) - RARRAY_LEN(ary2);
+    if (len == 0) return INT2FIX(0);
+    if (len > 0) return INT2FIX(1);
+    return INT2FIX(-1);
+}
+
+static VALUE
+ary_add_hash(VALUE hash, VALUE ary)
+{
+    long i;
+
+    for (i=0; i<RARRAY_LEN(ary); i++) {
+	VALUE elt = RARRAY_AREF(ary, i);
+	if (rb_hash_lookup2(hash, elt, Qundef) == Qundef) {
+	    rb_hash_aset(hash, elt, elt);
+	}
+    }
+    return hash;
+}
+
+static inline VALUE
+ary_tmp_hash_new(void)
+{
+    VALUE hash = rb_hash_new();
+
+    RBASIC_CLEAR_CLASS(hash);
+    return hash;
+}
+
+static VALUE
+ary_make_hash(VALUE ary)
+{
+    VALUE hash = ary_tmp_hash_new();
+    return ary_add_hash(hash, ary);
+}
+
+static VALUE
+ary_add_hash_by(VALUE hash, VALUE ary)
+{
+    long i;
+
+    for (i = 0; i < RARRAY_LEN(ary); ++i) {
+	VALUE v = rb_ary_elt(ary, i), k = rb_yield(v);
+	if (rb_hash_lookup2(hash, k, Qundef) == Qundef) {
+	    rb_hash_aset(hash, k, v);
+	}
+    }
+    return hash;
+}
+
+static VALUE
+ary_make_hash_by(VALUE ary)
+{
+    VALUE hash = ary_tmp_hash_new();
+    return ary_add_hash_by(hash, ary);
+}
+
+static inline void
+ary_recycle_hash(VALUE hash)
+{
+    if (RHASH(hash)->ntbl) {
+	st_table *tbl = RHASH(hash)->ntbl;
+	RHASH(hash)->ntbl = 0;
+	st_free_table(tbl);
+    }
+    RB_GC_GUARD(hash);
+}
+
+/*
+ *  call-seq:
+ *     ary - other_ary    -> new_ary
+ *
+ *  Array Difference
+ *
+ *  Returns a new array that is a copy of the original array, removing any
+ *  items that also appear in +other_ary+. The order is preserved from the
+ *  original array.
+ *
+ *  It compares elements using their #hash and #eql? methods for efficiency.
+ *
+ *     [ 1, 1, 2, 2, 3, 3, 4, 5 ] - [ 1, 2, 4 ]  #=>  [ 3, 3, 5 ]
+ *
+ *  If you need set-like behavior, see the library class Set.
+ */
+
+static VALUE
+rb_ary_diff(VALUE ary1, VALUE ary2)
+{
+    VALUE ary3;
+    VALUE hash;
+    long i;
+
+    hash = ary_make_hash(to_ary(ary2));
+    ary3 = rb_ary_new();
+
+    for (i=0; i<RARRAY_LEN(ary1); i++) {
+	if (st_lookup(rb_hash_tbl_raw(hash), RARRAY_AREF(ary1, i), 0)) continue;
+	rb_ary_push(ary3, rb_ary_elt(ary1, i));
+    }
+    ary_recycle_hash(hash);
+    return ary3;
+}
+
+/*
+ *  call-seq:
+ *     ary & other_ary      -> new_ary
+ *
+ *  Set Intersection --- Returns a new array containing elements common to the
+ *  two arrays, excluding any duplicates. The order is preserved from the
+ *  original array.
+ *
+ *  It compares elements using their #hash and #eql? methods for efficiency.
+ *
+ *     [ 1, 1, 3, 5 ] & [ 1, 2, 3 ]                 #=> [ 1, 3 ]
+ *     [ 'a', 'b', 'b', 'z' ] & [ 'a', 'b', 'c' ]   #=> [ 'a', 'b' ]
+ *
+ *  See also Array#uniq.
+ */
+
+
+static VALUE
+rb_ary_and(VALUE ary1, VALUE ary2)
+{
+    VALUE hash, ary3, v;
+    st_table *table;
+    st_data_t vv;
+    long i;
+
+    ary2 = to_ary(ary2);
+    ary3 = rb_ary_new();
+    if (RARRAY_LEN(ary2) == 0) return ary3;
+    hash = ary_make_hash(ary2);
+    table = rb_hash_tbl_raw(hash);
+
+    for (i=0; i<RARRAY_LEN(ary1); i++) {
+	v = RARRAY_AREF(ary1, i);
+	vv = (st_data_t)v;
+	if (st_delete(table, &vv, 0)) {
+	    rb_ary_push(ary3, v);
+	}
+    }
+    ary_recycle_hash(hash);
+
+    return ary3;
+}
+
+static int
+ary_hash_orset(st_data_t *key, st_data_t *value, st_data_t arg, int existing)
+{
+    if (existing) return ST_STOP;
+    *key = *value = (VALUE)arg;
+    return ST_CONTINUE;
+}
+
+/*
+ *  call-seq:
+ *     ary | other_ary     -> new_ary
+ *
+ *  Set Union --- Returns a new array by joining +ary+ with +other_ary+,
+ *  excluding any duplicates and preserving the order from the original array.
+ *
+ *  It compares elements using their #hash and #eql? methods for efficiency.
+ *
+ *     [ "a", "b", "c" ] | [ "c", "d", "a" ]    #=> [ "a", "b", "c", "d" ]
+ *
+ *  See also Array#uniq.
+ */
+
+static VALUE
+rb_ary_or(VALUE ary1, VALUE ary2)
+{
+    VALUE hash, ary3;
+    long i;
+
+    ary2 = to_ary(ary2);
+    hash = ary_make_hash(ary1);
+
+    for (i=0; i<RARRAY_LEN(ary2); i++) {
+	VALUE elt = RARRAY_AREF(ary2, i);
+	if (!st_update(RHASH_TBL_RAW(hash), (st_data_t)elt, ary_hash_orset, (st_data_t)elt)) {
+	    RB_OBJ_WRITTEN(hash, Qundef, elt);
+	}
+    }
+    ary3 = rb_hash_values(hash);
+    ary_recycle_hash(hash);
+    return ary3;
+}
+
+static int
+push_value(st_data_t key, st_data_t val, st_data_t ary)
+{
+    rb_ary_push((VALUE)ary, (VALUE)val);
+    return ST_CONTINUE;
+}
+
+/*
+ *  call-seq:
+ *     ary.uniq!                -> ary or nil
+ *     ary.uniq! { |item| ... } -> ary or nil
+ *
+ *  Removes duplicate elements from +self+.
+ *
+ *  If a block is given, it will use the return value of the block for
+ *  comparison.
+ *
+ *  It compares values using their #hash and #eql? methods for efficiency.
+ *
+ *  Returns +nil+ if no changes are made (that is, no duplicates are found).
+ *
+ *     a = [ "a", "a", "b", "b", "c" ]
+ *     a.uniq!   # => ["a", "b", "c"]
+ *
+ *     b = [ "a", "b", "c" ]
+ *     b.uniq!   # => nil
+ *
+ *     c = [["student","sam"], ["student","george"], ["teacher","matz"]]
+ *     c.uniq! { |s| s.first } # => [["student", "sam"], ["teacher", "matz"]]
+ *
+ */
+
+static VALUE
+rb_ary_uniq_bang(VALUE ary)
+{
+    VALUE hash;
+    long hash_size;
+
+    rb_ary_modify_check(ary);
+    if (RARRAY_LEN(ary) <= 1)
+        return Qnil;
+    if (rb_block_given_p())
+	hash = ary_make_hash_by(ary);
+    else
+	hash = ary_make_hash(ary);
+
+    hash_size = RHASH_SIZE(hash);
+    if (RARRAY_LEN(ary) == hash_size) {
+	return Qnil;
+    }
+    rb_ary_modify_check(ary);
+    ARY_SET_LEN(ary, 0);
+    if (ARY_SHARED_P(ary) && !ARY_EMBED_P(ary)) {
+	rb_ary_unshare(ary);
+	FL_SET_EMBED(ary);
+    }
+    ary_resize_capa(ary, hash_size);
+    st_foreach(rb_hash_tbl_raw(hash), push_value, ary);
+    ary_recycle_hash(hash);
+
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.uniq                -> new_ary
+ *     ary.uniq { |item| ... } -> new_ary
+ *
+ *  Returns a new array by removing duplicate values in +self+.
+ *
+ *  If a block is given, it will use the return value of the block for comparison.
+ *
+ *  It compares values using their #hash and #eql? methods for efficiency.
+ *
+ *     a = [ "a", "a", "b", "b", "c" ]
+ *     a.uniq   # => ["a", "b", "c"]
+ *
+ *     b = [["student","sam"], ["student","george"], ["teacher","matz"]]
+ *     b.uniq { |s| s.first } # => [["student", "sam"], ["teacher", "matz"]]
+ *
+ */
+
+static VALUE
+rb_ary_uniq(VALUE ary)
+{
+    VALUE hash, uniq;
+
+    if (RARRAY_LEN(ary) <= 1)
+        return rb_ary_dup(ary);
+    if (rb_block_given_p()) {
+	hash = ary_make_hash_by(ary);
+	uniq = rb_hash_values(hash);
+    }
+    else {
+	hash = ary_make_hash(ary);
+	uniq = rb_hash_values(hash);
+    }
+    RBASIC_SET_CLASS(uniq, rb_obj_class(ary));
+    ary_recycle_hash(hash);
+
+    return uniq;
+}
+
+/*
+ *  call-seq:
+ *     ary.compact!    -> ary  or  nil
+ *
+ *  Removes +nil+ elements from the array.
+ *
+ *  Returns +nil+ if no changes were made, otherwise returns the array.
+ *
+ *     [ "a", nil, "b", nil, "c" ].compact! #=> [ "a", "b", "c" ]
+ *     [ "a", "b", "c" ].compact!           #=> nil
+ */
+
+static VALUE
+rb_ary_compact_bang(VALUE ary)
+{
+    VALUE *p, *t, *end;
+    long n;
+
+    rb_ary_modify(ary);
+    p = t = (VALUE *)RARRAY_CONST_PTR(ary); /* WB: no new reference */
+    end = p + RARRAY_LEN(ary);
+
+    while (t < end) {
+	if (NIL_P(*t)) t++;
+	else *p++ = *t++;
+    }
+    n = p - RARRAY_CONST_PTR(ary);
+    if (RARRAY_LEN(ary) == n) {
+	return Qnil;
+    }
+    ary_resize_smaller(ary, n);
+
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.compact     -> new_ary
+ *
+ *  Returns a copy of +self+ with all +nil+ elements removed.
+ *
+ *     [ "a", nil, "b", nil, "c", nil ].compact
+ *                       #=> [ "a", "b", "c" ]
+ */
+
+static VALUE
+rb_ary_compact(VALUE ary)
+{
+    ary = rb_ary_dup(ary);
+    rb_ary_compact_bang(ary);
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.count                   -> int
+ *     ary.count(obj)              -> int
+ *     ary.count { |item| block }  -> int
+ *
+ *  Returns the number of elements.
+ *
+ *  If an argument is given, counts the number of elements which equal +obj+
+ *  using <code>==</code>.
+ *
+ *  If a block is given, counts the number of elements for which the block
+ *  returns a true value.
+ *
+ *     ary = [1, 2, 4, 2]
+ *     ary.count                  #=> 4
+ *     ary.count(2)               #=> 2
+ *     ary.count { |x| x%2 == 0 } #=> 3
+ *
+ */
+
+static VALUE
+rb_ary_count(int argc, VALUE *argv, VALUE ary)
+{
+    long i, n = 0;
+
+    if (argc == 0) {
+	VALUE v;
+
+	if (!rb_block_given_p())
+	    return LONG2NUM(RARRAY_LEN(ary));
+
+	for (i = 0; i < RARRAY_LEN(ary); i++) {
+	    v = RARRAY_AREF(ary, i);
+	    if (RTEST(rb_yield(v))) n++;
+	}
+    }
+    else {
+	VALUE obj;
+
+	rb_scan_args(argc, argv, "1", &obj);
+	if (rb_block_given_p()) {
+	    rb_warn("given block not used");
+	}
+	for (i = 0; i < RARRAY_LEN(ary); i++) {
+	    if (rb_equal(RARRAY_AREF(ary, i), obj)) n++;
+	}
+    }
+
+    return LONG2NUM(n);
+}
+
+static VALUE
+flatten(VALUE ary, int level, int *modified)
+{
+    long i = 0;
+    VALUE stack, result, tmp, elt;
+    st_table *memo;
+    st_data_t id;
+
+    stack = ary_new(0, ARY_DEFAULT_SIZE);
+    result = ary_new(0, RARRAY_LEN(ary));
+    memo = st_init_numtable();
+    st_insert(memo, (st_data_t)ary, (st_data_t)Qtrue);
+    *modified = 0;
+
+    while (1) {
+	while (i < RARRAY_LEN(ary)) {
+	    elt = RARRAY_AREF(ary, i++);
+	    tmp = rb_check_array_type(elt);
+	    if (RBASIC(result)->klass) {
+		rb_raise(rb_eRuntimeError, "flatten reentered");
+	    }
+	    if (NIL_P(tmp) || (level >= 0 && RARRAY_LEN(stack) / 2 >= level)) {
+		rb_ary_push(result, elt);
+	    }
+	    else {
+		*modified = 1;
+		id = (st_data_t)tmp;
+		if (st_lookup(memo, id, 0)) {
+		    st_free_table(memo);
+		    rb_raise(rb_eArgError, "tried to flatten recursive array");
+		}
+		st_insert(memo, id, (st_data_t)Qtrue);
+		rb_ary_push(stack, ary);
+		rb_ary_push(stack, LONG2NUM(i));
+		ary = tmp;
+		i = 0;
+	    }
+	}
+	if (RARRAY_LEN(stack) == 0) {
+	    break;
+	}
+	id = (st_data_t)ary;
+	st_delete(memo, &id, 0);
+	tmp = rb_ary_pop(stack);
+	i = NUM2LONG(tmp);
+	ary = rb_ary_pop(stack);
+    }
+
+    st_free_table(memo);
+
+    RBASIC_SET_CLASS(result, rb_class_of(ary));
+    return result;
+}
+
+/*
+ *  call-seq:
+ *     ary.flatten!        -> ary or nil
+ *     ary.flatten!(level) -> ary or nil
+ *
+ *  Flattens +self+ in place.
+ *
+ *  Returns +nil+ if no modifications were made (i.e., the array contains no
+ *  subarrays.)
+ *
+ *  The optional +level+ argument determines the level of recursion to flatten.
+ *
+ *     a = [ 1, 2, [3, [4, 5] ] ]
+ *     a.flatten!   #=> [1, 2, 3, 4, 5]
+ *     a.flatten!   #=> nil
+ *     a            #=> [1, 2, 3, 4, 5]
+ *     a = [ 1, 2, [3, [4, 5] ] ]
+ *     a.flatten!(1) #=> [1, 2, 3, [4, 5]]
+ */
+
+static VALUE
+rb_ary_flatten_bang(int argc, VALUE *argv, VALUE ary)
+{
+    int mod = 0, level = -1;
+    VALUE result, lv;
+
+    rb_scan_args(argc, argv, "01", &lv);
+    rb_ary_modify_check(ary);
+    if (!NIL_P(lv)) level = NUM2INT(lv);
+    if (level == 0) return Qnil;
+
+    result = flatten(ary, level, &mod);
+    if (mod == 0) {
+	ary_discard(result);
+	return Qnil;
+    }
+    if (!(mod = ARY_EMBED_P(result))) rb_obj_freeze(result);
+    rb_ary_replace(ary, result);
+    if (mod) ARY_SET_EMBED_LEN(result, 0);
+
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.flatten -> new_ary
+ *     ary.flatten(level) -> new_ary
+ *
+ *  Returns a new array that is a one-dimensional flattening of +self+
+ *  (recursively).
+ *
+ *  That is, for every element that is an array, extract its elements into
+ *  the new array.
+ *
+ *  The optional +level+ argument determines the level of recursion to
+ *  flatten.
+ *
+ *     s = [ 1, 2, 3 ]           #=> [1, 2, 3]
+ *     t = [ 4, 5, 6, [7, 8] ]   #=> [4, 5, 6, [7, 8]]
+ *     a = [ s, t, 9, 10 ]       #=> [[1, 2, 3], [4, 5, 6, [7, 8]], 9, 10]
+ *     a.flatten                 #=> [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+ *     a = [ 1, 2, [3, [4, 5] ] ]
+ *     a.flatten(1)              #=> [1, 2, 3, [4, 5]]
+ */
+
+static VALUE
+rb_ary_flatten(int argc, VALUE *argv, VALUE ary)
+{
+    int mod = 0, level = -1;
+    VALUE result, lv;
+
+    rb_scan_args(argc, argv, "01", &lv);
+    if (!NIL_P(lv)) level = NUM2INT(lv);
+    if (level == 0) return ary_make_shared_copy(ary);
+
+    result = flatten(ary, level, &mod);
+    OBJ_INFECT(result, ary);
+
+    return result;
+}
+
+#define OPTHASH_GIVEN_P(opts) \
+    (argc > 0 && !NIL_P((opts) = rb_check_hash_type(argv[argc-1])) && (--argc, 1))
+static ID id_random;
+
+#define RAND_UPTO(max) (long)rb_random_ulong_limited((randgen), (max)-1)
+
+/*
+ *  call-seq:
+ *     ary.shuffle!              -> ary
+ *     ary.shuffle!(random: rng) -> ary
+ *
+ *  Shuffles elements in +self+ in place.
+ *
+ *     a = [ 1, 2, 3 ]           #=> [1, 2, 3]
+ *     a.shuffle!                #=> [2, 3, 1]
+ *     a                         #=> [2, 3, 1]
+ *
+ *  The optional +rng+ argument will be used as the random number generator.
+ *
+ *     a.shuffle!(random: Random.new(1))  #=> [1, 3, 2]
+ */
+
+static VALUE
+rb_ary_shuffle_bang(int argc, VALUE *argv, VALUE ary)
+{
+    VALUE opts, randgen = rb_cRandom;
+    long i, len;
+
+    if (OPTHASH_GIVEN_P(opts)) {
+	VALUE rnd;
+	ID keyword_ids[1];
+
+	keyword_ids[0] = id_random;
+	rb_get_kwargs(opts, keyword_ids, 0, 1, &rnd);
+	if (rnd != Qundef) {
+	    randgen = rnd;
+	}
+    }
+    rb_check_arity(argc, 0, 0);
+    rb_ary_modify(ary);
+    i = len = RARRAY_LEN(ary);
+    RARRAY_PTR_USE(ary, ptr, {
+	while (i) {
+	    long j = RAND_UPTO(i);
+	    VALUE tmp;
+	    if (len != RARRAY_LEN(ary) || ptr != RARRAY_CONST_PTR(ary)) {
+		rb_raise(rb_eRuntimeError, "modified during shuffle");
+	    }
+	    tmp = ptr[--i];
+	    ptr[i] = ptr[j];
+	    ptr[j] = tmp;
+	}
+    }); /* WB: no new reference */
+    return ary;
+}
+
+
+/*
+ *  call-seq:
+ *     ary.shuffle              -> new_ary
+ *     ary.shuffle(random: rng) -> new_ary
+ *
+ *  Returns a new array with elements of +self+ shuffled.
+ *
+ *     a = [ 1, 2, 3 ]           #=> [1, 2, 3]
+ *     a.shuffle                 #=> [2, 3, 1]
+ *     a                         #=> [1, 2, 3]
+ *
+ *  The optional +rng+ argument will be used as the random number generator.
+ *
+ *     a.shuffle(random: Random.new(1))  #=> [1, 3, 2]
+ */
+
+static VALUE
+rb_ary_shuffle(int argc, VALUE *argv, VALUE ary)
+{
+    ary = rb_ary_dup(ary);
+    rb_ary_shuffle_bang(argc, argv, ary);
+    return ary;
+}
+
+
+/*
+ *  call-seq:
+ *     ary.sample                  -> obj
+ *     ary.sample(random: rng)     -> obj
+ *     ary.sample(n)               -> new_ary
+ *     ary.sample(n, random: rng)  -> new_ary
+ *
+ *  Choose a random element or +n+ random elements from the array.
+ *
+ *  The elements are chosen by using random and unique indices into the array
+ *  in order to ensure that an element doesn't repeat itself unless the array
+ *  already contained duplicate elements.
+ *
+ *  If the array is empty the first form returns +nil+ and the second form
+ *  returns an empty array.
+ *
+ *  The optional +rng+ argument will be used as the random number generator.
+ *
+ *     a = [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ]
+ *     a.sample         #=> 7
+ *     a.sample(4)      #=> [6, 4, 2, 5]
+ */
+
+
+static VALUE
+rb_ary_sample(int argc, VALUE *argv, VALUE ary)
+{
+    VALUE nv, result;
+    VALUE opts, randgen = rb_cRandom;
+    long n, len, i, j, k, idx[10];
+    long rnds[numberof(idx)];
+
+    if (OPTHASH_GIVEN_P(opts)) {
+	VALUE rnd;
+	ID keyword_ids[1];
+
+	keyword_ids[0] = id_random;
+	rb_get_kwargs(opts, keyword_ids, 0, 1, &rnd);
+	if (rnd != Qundef) {
+	    randgen = rnd;
+	}
+    }
+    len = RARRAY_LEN(ary);
+    if (argc == 0) {
+	if (len < 2)
+	    i = 0;
+	else
+	    i = RAND_UPTO(len);
+
+	return rb_ary_elt(ary, i);
+    }
+    rb_scan_args(argc, argv, "1", &nv);
+    n = NUM2LONG(nv);
+    if (n < 0) rb_raise(rb_eArgError, "negative sample number");
+    if (n > len) n = len;
+    if (n <= numberof(idx)) {
+	for (i = 0; i < n; ++i) {
+	    rnds[i] = RAND_UPTO(len - i);
+	}
+    }
+    k = len;
+    len = RARRAY_LEN(ary);
+    if (len < k && n <= numberof(idx)) {
+	for (i = 0; i < n; ++i) {
+	    if (rnds[i] >= len) return rb_ary_new_capa(0);
+	}
+    }
+    if (n > len) n = len;
+    switch (n) {
+      case 0:
+	return rb_ary_new_capa(0);
+      case 1:
+	i = rnds[0];
+	return rb_ary_new_from_values(1, &RARRAY_AREF(ary, i));
+      case 2:
+	i = rnds[0];
+	j = rnds[1];
+	if (j >= i) j++;
+	return rb_ary_new_from_args(2, RARRAY_AREF(ary, i), RARRAY_AREF(ary, j));
+      case 3:
+	i = rnds[0];
+	j = rnds[1];
+	k = rnds[2];
+	{
+	    long l = j, g = i;
+	    if (j >= i) l = i, g = ++j;
+	    if (k >= l && (++k >= g)) ++k;
+	}
+	return rb_ary_new_from_args(3, RARRAY_AREF(ary, i), RARRAY_AREF(ary, j), RARRAY_AREF(ary, k));
+    }
+    if (n <= numberof(idx)) {
+	long sorted[numberof(idx)];
+	sorted[0] = idx[0] = rnds[0];
+	for (i=1; i<n; i++) {
+	    k = rnds[i];
+	    for (j = 0; j < i; ++j) {
+		if (k < sorted[j]) break;
+		++k;
+	    }
+	    memmove(&sorted[j+1], &sorted[j], sizeof(sorted[0])*(i-j));
+	    sorted[j] = idx[i] = k;
+	}
+	result = rb_ary_new_capa(n);
+	RARRAY_PTR_USE(result, ptr_result, {
+	    for (i=0; i<n; i++) {
+		ptr_result[i] = RARRAY_AREF(ary, idx[i]);
+	    }
+	});
+    }
+    else {
+	result = rb_ary_dup(ary);
+	RBASIC_CLEAR_CLASS(result);
+	RB_GC_GUARD(ary);
+	RARRAY_PTR_USE(result, ptr_result, {
+	    for (i=0; i<n; i++) {
+		j = RAND_UPTO(len-i) + i;
+		nv = ptr_result[j];
+		ptr_result[j] = ptr_result[i];
+		ptr_result[i] = nv;
+	    }
+	});
+	RBASIC_SET_CLASS_RAW(result, rb_cArray);
+    }
+    ARY_SET_LEN(result, n);
+
+    return result;
+}
+
+static VALUE
+rb_ary_cycle_size(VALUE self, VALUE args, VALUE eobj)
+{
+    long mul;
+    VALUE n = Qnil;
+    if (args && (RARRAY_LEN(args) > 0)) {
+	n = RARRAY_AREF(args, 0);
+    }
+    if (RARRAY_LEN(self) == 0) return INT2FIX(0);
+    if (n == Qnil) return DBL2NUM(INFINITY);
+    mul = NUM2LONG(n);
+    if (mul <= 0) return INT2FIX(0);
+    n = LONG2FIX(mul);
+    return rb_funcallv(rb_ary_length(self), '*', 1, &n);
+}
+
+/*
+ *  call-seq:
+ *     ary.cycle(n=nil) { |obj| block }  -> nil
+ *     ary.cycle(n=nil)                  -> Enumerator
+ *
+ *  Calls the given block for each element +n+ times or forever if +nil+ is
+ *  given.
+ *
+ *  Does nothing if a non-positive number is given or the array is empty.
+ *
+ *  Returns +nil+ if the loop has finished without getting interrupted.
+ *
+ *  If no block is given, an Enumerator is returned instead.
+ *
+ *     a = ["a", "b", "c"]
+ *     a.cycle { |x| puts x }     # print, a, b, c, a, b, c,.. forever.
+ *     a.cycle(2) { |x| puts x }  # print, a, b, c, a, b, c.
+ *
+ */
+
+static VALUE
+rb_ary_cycle(int argc, VALUE *argv, VALUE ary)
+{
+    long n, i;
+    VALUE nv = Qnil;
+
+    rb_scan_args(argc, argv, "01", &nv);
+
+    RETURN_SIZED_ENUMERATOR(ary, argc, argv, rb_ary_cycle_size);
+    if (NIL_P(nv)) {
+        n = -1;
+    }
+    else {
+        n = NUM2LONG(nv);
+        if (n <= 0) return Qnil;
+    }
+
+    while (RARRAY_LEN(ary) > 0 && (n < 0 || 0 < n--)) {
+        for (i=0; i<RARRAY_LEN(ary); i++) {
+            rb_yield(RARRAY_AREF(ary, i));
+        }
+    }
+    return Qnil;
+}
+
+#define tmpbuf(n, size) rb_str_tmp_new((n)*(size))
+#define tmpbuf_discard(s) (rb_str_resize((s), 0L), RBASIC_SET_CLASS_RAW(s, rb_cString))
+#define tmpary(n) rb_ary_tmp_new(n)
+#define tmpary_discard(a) (ary_discard(a), RBASIC_SET_CLASS_RAW(a, rb_cArray))
+
+/*
+ * Build a ruby array of the corresponding values and yield it to the
+ * associated block.
+ * Return the class of +values+ for reentry check.
+ */
+static int
+yield_indexed_values(const VALUE values, const long r, const long *const p)
+{
+    const VALUE result = rb_ary_new2(r);
+    VALUE *const result_array = RARRAY_PTR(result);
+    const VALUE *const values_array = RARRAY_CONST_PTR(values);
+    long i;
+
+    for (i = 0; i < r; i++) result_array[i] = values_array[p[i]];
+    ARY_SET_LEN(result, r);
+    rb_yield(result);
+    return !RBASIC(values)->klass;
+}
+
+/*
+ * Compute permutations of +r+ elements of the set <code>[0..n-1]</code>.
+ *
+ * When we have a complete permutation of array indexes, copy the values
+ * at those indexes into a new array and yield that array.
+ *
+ * n: the size of the set
+ * r: the number of elements in each permutation
+ * p: the array (of size r) that we're filling in
+ * used: an array of booleans: whether a given index is already used
+ * values: the Ruby array that holds the actual values to permute
+ */
+static void
+permute0(const long n, const long r, long *const p, char *const used, const VALUE values)
+{
+    long i = 0, index = 0;
+
+    for (;;) {
+	const char *const unused = memchr(&used[i], 0, n-i);
+	if (!unused) {
+	    if (!index) break;
+	    i = p[--index];                /* pop index */
+	    used[i++] = 0;                 /* index unused */
+	}
+	else {
+	    i = unused - used;
+	    p[index] = i;
+	    used[i] = 1;                   /* mark index used */
+	    ++index;
+	    if (index < r-1) {             /* if not done yet */
+		p[index] = i = 0;
+		continue;
+	    }
+	    for (i = 0; i < n; ++i) {
+		if (used[i]) continue;
+		p[index] = i;
+		if (!yield_indexed_values(values, r, p)) {
+		    rb_raise(rb_eRuntimeError, "permute reentered");
+		}
+	    }
+	    i = p[--index];                /* pop index */
+	    used[i] = 0;                   /* index unused */
+	    p[index] = ++i;
+	}
+    }
+}
+
+/*
+ * Returns the product of from, from-1, ..., from - how_many + 1.
+ * http://en.wikipedia.org/wiki/Pochhammer_symbol
+ */
+static VALUE
+descending_factorial(long from, long how_many)
+{
+    VALUE cnt = LONG2FIX(how_many >= 0);
+    while (how_many-- > 0) {
+	VALUE v = LONG2FIX(from--);
+	cnt = rb_funcallv(cnt, '*', 1, &v);
+    }
+    return cnt;
+}
+
+static VALUE
+binomial_coefficient(long comb, long size)
+{
+    VALUE r, v;
+    if (comb > size-comb) {
+	comb = size-comb;
+    }
+    if (comb < 0) {
+	return LONG2FIX(0);
+    }
+    r = descending_factorial(size, comb);
+    v = descending_factorial(comb, comb);
+    return rb_funcallv(r, id_div, 1, &v);
+}
+
+static VALUE
+rb_ary_permutation_size(VALUE ary, VALUE args, VALUE eobj)
+{
+    long n = RARRAY_LEN(ary);
+    long k = (args && (RARRAY_LEN(args) > 0)) ? NUM2LONG(RARRAY_AREF(args, 0)) : n;
+
+    return descending_factorial(n, k);
+}
+
+/*
+ *  call-seq:
+ *     ary.permutation { |p| block }          -> ary
+ *     ary.permutation                        -> Enumerator
+ *     ary.permutation(n) { |p| block }       -> ary
+ *     ary.permutation(n)                     -> Enumerator
+ *
+ * When invoked with a block, yield all permutations of length +n+ of the
+ * elements of the array, then return the array itself.
+ *
+ * If +n+ is not specified, yield all permutations of all elements.
+ *
+ * The implementation makes no guarantees about the order in which the
+ * permutations are yielded.
+ *
+ * If no block is given, an Enumerator is returned instead.
+ *
+ * Examples:
+ *
+ *   a = [1, 2, 3]
+ *   a.permutation.to_a    #=> [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
+ *   a.permutation(1).to_a #=> [[1],[2],[3]]
+ *   a.permutation(2).to_a #=> [[1,2],[1,3],[2,1],[2,3],[3,1],[3,2]]
+ *   a.permutation(3).to_a #=> [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]
+ *   a.permutation(0).to_a #=> [[]] # one permutation of length 0
+ *   a.permutation(4).to_a #=> []   # no permutations of length 4
+ */
+
+static VALUE
+rb_ary_permutation(int argc, VALUE *argv, VALUE ary)
+{
+    VALUE num;
+    long r, n, i;
+
+    n = RARRAY_LEN(ary);                  /* Array length */
+    RETURN_SIZED_ENUMERATOR(ary, argc, argv, rb_ary_permutation_size);   /* Return enumerator if no block */
+    rb_scan_args(argc, argv, "01", &num);
+    r = NIL_P(num) ? n : NUM2LONG(num);   /* Permutation size from argument */
+
+    if (r < 0 || n < r) {
+	/* no permutations: yield nothing */
+    }
+    else if (r == 0) { /* exactly one permutation: the zero-length array */
+	rb_yield(rb_ary_new2(0));
+    }
+    else if (r == 1) { /* this is a special, easy case */
+	for (i = 0; i < RARRAY_LEN(ary); i++) {
+	    rb_yield(rb_ary_new3(1, RARRAY_AREF(ary, i)));
+	}
+    }
+    else {             /* this is the general case */
+	volatile VALUE t0;
+	long *p = (long*)ALLOCV(t0, r*sizeof(long)+n*sizeof(char));
+	char *used = (char*)(p + r);
+	VALUE ary0 = ary_make_shared_copy(ary); /* private defensive copy of ary */
+	RBASIC_CLEAR_CLASS(ary0);
+
+	MEMZERO(used, char, n); /* initialize array */
+
+	permute0(n, r, p, used, ary0); /* compute and yield permutations */
+	ALLOCV_END(t0);
+	RBASIC_SET_CLASS_RAW(ary0, rb_cArray);
+    }
+    return ary;
+}
+
+static void
+combinate0(const long len, const long n, long *const stack, const VALUE values)
+{
+    long lev = 0;
+
+    MEMZERO(stack+1, long, n);
+    stack[0] = -1;
+    for (;;) {
+	for (lev++; lev < n; lev++) {
+	    stack[lev+1] = stack[lev]+1;
+	}
+	if (!yield_indexed_values(values, n, stack+1)) {
+	    rb_raise(rb_eRuntimeError, "combination reentered");
+	}
+	do {
+	    if (lev == 0) return;
+	    stack[lev--]++;
+	} while (stack[lev+1]+n == len+lev+1);
+    }
+}
+
+static VALUE
+rb_ary_combination_size(VALUE ary, VALUE args, VALUE eobj)
+{
+    long n = RARRAY_LEN(ary);
+    long k = NUM2LONG(RARRAY_AREF(args, 0));
+
+    return binomial_coefficient(k, n);
+}
+
+/*
+ *  call-seq:
+ *     ary.combination(n) { |c| block }    -> ary
+ *     ary.combination(n)                  -> Enumerator
+ *
+ * When invoked with a block, yields all combinations of length +n+ of elements
+ * from the array and then returns the array itself.
+ *
+ * The implementation makes no guarantees about the order in which the
+ * combinations are yielded.
+ *
+ * If no block is given, an Enumerator is returned instead.
+ *
+ * Examples:
+ *
+ *     a = [1, 2, 3, 4]
+ *     a.combination(1).to_a  #=> [[1],[2],[3],[4]]
+ *     a.combination(2).to_a  #=> [[1,2],[1,3],[1,4],[2,3],[2,4],[3,4]]
+ *     a.combination(3).to_a  #=> [[1,2,3],[1,2,4],[1,3,4],[2,3,4]]
+ *     a.combination(4).to_a  #=> [[1,2,3,4]]
+ *     a.combination(0).to_a  #=> [[]] # one combination of length 0
+ *     a.combination(5).to_a  #=> []   # no combinations of length 5
+ *
+ */
+
+static VALUE
+rb_ary_combination(VALUE ary, VALUE num)
+{
+    long i, n, len;
+
+    n = NUM2LONG(num);
+    RETURN_SIZED_ENUMERATOR(ary, 1, &num, rb_ary_combination_size);
+    len = RARRAY_LEN(ary);
+    if (n < 0 || len < n) {
+	/* yield nothing */
+    }
+    else if (n == 0) {
+	rb_yield(rb_ary_new2(0));
+    }
+    else if (n == 1) {
+	for (i = 0; i < len; i++) {
+	    rb_yield(rb_ary_new3(1, RARRAY_AREF(ary, i)));
+	}
+    }
+    else {
+	VALUE ary0 = ary_make_shared_copy(ary); /* private defensive copy of ary */
+	volatile VALUE t0;
+	long *stack = ALLOCV_N(long, t0, n+1);
+
+	RBASIC_CLEAR_CLASS(ary0);
+	combinate0(len, n, stack, ary0);
+	ALLOCV_END(t0);
+	RBASIC_SET_CLASS_RAW(ary0, rb_cArray);
+    }
+    return ary;
+}
+
+/*
+ * Compute repeated permutations of +r+ elements of the set
+ * <code>[0..n-1]</code>.
+ *
+ * When we have a complete repeated permutation of array indexes, copy the
+ * values at those indexes into a new array and yield that array.
+ *
+ * n: the size of the set
+ * r: the number of elements in each permutation
+ * p: the array (of size r) that we're filling in
+ * values: the Ruby array that holds the actual values to permute
+ */
+static void
+rpermute0(const long n, const long r, long *const p, const VALUE values)
+{
+    long i = 0, index = 0;
+
+    p[index] = i;
+    for (;;) {
+	if (++index < r-1) {
+	    p[index] = i = 0;
+	    continue;
+	}
+	for (i = 0; i < n; ++i) {
+	    p[index] = i;
+	    if (!yield_indexed_values(values, r, p)) {
+		rb_raise(rb_eRuntimeError, "repeated permute reentered");
+	    }
+	}
+	do {
+	    if (index <= 0) return;
+	} while ((i = ++p[--index]) >= n);
+    }
+}
+
+static VALUE
+rb_ary_repeated_permutation_size(VALUE ary, VALUE args, VALUE eobj)
+{
+    long n = RARRAY_LEN(ary);
+    long k = NUM2LONG(RARRAY_AREF(args, 0));
+    VALUE v;
+
+    if (k < 0) {
+	return LONG2FIX(0);
+    }
+
+    v = LONG2NUM(k);
+    return rb_funcallv(LONG2NUM(n), id_power, 1, &v);
+}
+
+/*
+ *  call-seq:
+ *     ary.repeated_permutation(n) { |p| block } -> ary
+ *     ary.repeated_permutation(n)               -> Enumerator
+ *
+ * When invoked with a block, yield all repeated permutations of length +n+ of
+ * the elements of the array, then return the array itself.
+ *
+ * The implementation makes no guarantees about the order in which the repeated
+ * permutations are yielded.
+ *
+ * If no block is given, an Enumerator is returned instead.
+ *
+ * Examples:
+ *
+ *     a = [1, 2]
+ *     a.repeated_permutation(1).to_a  #=> [[1], [2]]
+ *     a.repeated_permutation(2).to_a  #=> [[1,1],[1,2],[2,1],[2,2]]
+ *     a.repeated_permutation(3).to_a  #=> [[1,1,1],[1,1,2],[1,2,1],[1,2,2],
+ *                                     #    [2,1,1],[2,1,2],[2,2,1],[2,2,2]]
+ *     a.repeated_permutation(0).to_a  #=> [[]] # one permutation of length 0
+ */
+
+static VALUE
+rb_ary_repeated_permutation(VALUE ary, VALUE num)
+{
+    long r, n, i;
+
+    n = RARRAY_LEN(ary);                  /* Array length */
+    RETURN_SIZED_ENUMERATOR(ary, 1, &num, rb_ary_repeated_permutation_size);      /* Return Enumerator if no block */
+    r = NUM2LONG(num);                    /* Permutation size from argument */
+
+    if (r < 0) {
+	/* no permutations: yield nothing */
+    }
+    else if (r == 0) { /* exactly one permutation: the zero-length array */
+	rb_yield(rb_ary_new2(0));
+    }
+    else if (r == 1) { /* this is a special, easy case */
+	for (i = 0; i < RARRAY_LEN(ary); i++) {
+	    rb_yield(rb_ary_new3(1, RARRAY_AREF(ary, i)));
+	}
+    }
+    else {             /* this is the general case */
+	volatile VALUE t0;
+	long *p = ALLOCV_N(long, t0, r);
+	VALUE ary0 = ary_make_shared_copy(ary); /* private defensive copy of ary */
+	RBASIC_CLEAR_CLASS(ary0);
+
+	rpermute0(n, r, p, ary0); /* compute and yield repeated permutations */
+	ALLOCV_END(t0);
+	RBASIC_SET_CLASS_RAW(ary0, rb_cArray);
+    }
+    return ary;
+}
+
+static void
+rcombinate0(const long n, const long r, long *const p, const long rest, const VALUE values)
+{
+    long i = 0, index = 0;
+
+    p[index] = i;
+    for (;;) {
+	if (++index < r-1) {
+	    p[index] = i;
+	    continue;
+	}
+	for (; i < n; ++i) {
+	    p[index] = i;
+	    if (!yield_indexed_values(values, r, p)) {
+		rb_raise(rb_eRuntimeError, "repeated combination reentered");
+	    }
+	}
+	do {
+	    if (index <= 0) return;
+	} while ((i = ++p[--index]) >= n);
+    }
+}
+
+static VALUE
+rb_ary_repeated_combination_size(VALUE ary, VALUE args, VALUE eobj)
+{
+    long n = RARRAY_LEN(ary);
+    long k = NUM2LONG(RARRAY_AREF(args, 0));
+    if (k == 0) {
+	return LONG2FIX(1);
+    }
+    return binomial_coefficient(k, n + k - 1);
+}
+
+/*
+ *  call-seq:
+ *     ary.repeated_combination(n) { |c| block } -> ary
+ *     ary.repeated_combination(n)               -> Enumerator
+ *
+ * When invoked with a block, yields all repeated combinations of length +n+ of
+ * elements from the array and then returns the array itself.
+ *
+ * The implementation makes no guarantees about the order in which the repeated
+ * combinations are yielded.
+ *
+ * If no block is given, an Enumerator is returned instead.
+ *
+ * Examples:
+ *
+ *   a = [1, 2, 3]
+ *   a.repeated_combination(1).to_a  #=> [[1], [2], [3]]
+ *   a.repeated_combination(2).to_a  #=> [[1,1],[1,2],[1,3],[2,2],[2,3],[3,3]]
+ *   a.repeated_combination(3).to_a  #=> [[1,1,1],[1,1,2],[1,1,3],[1,2,2],[1,2,3],
+ *                                   #    [1,3,3],[2,2,2],[2,2,3],[2,3,3],[3,3,3]]
+ *   a.repeated_combination(4).to_a  #=> [[1,1,1,1],[1,1,1,2],[1,1,1,3],[1,1,2,2],[1,1,2,3],
+ *                                   #    [1,1,3,3],[1,2,2,2],[1,2,2,3],[1,2,3,3],[1,3,3,3],
+ *                                   #    [2,2,2,2],[2,2,2,3],[2,2,3,3],[2,3,3,3],[3,3,3,3]]
+ *   a.repeated_combination(0).to_a  #=> [[]] # one combination of length 0
+ *
+ */
+
+static VALUE
+rb_ary_repeated_combination(VALUE ary, VALUE num)
+{
+    long n, i, len;
+
+    n = NUM2LONG(num);                 /* Combination size from argument */
+    RETURN_SIZED_ENUMERATOR(ary, 1, &num, rb_ary_repeated_combination_size);   /* Return enumerator if no block */
+    len = RARRAY_LEN(ary);
+    if (n < 0) {
+	/* yield nothing */
+    }
+    else if (n == 0) {
+	rb_yield(rb_ary_new2(0));
+    }
+    else if (n == 1) {
+	for (i = 0; i < len; i++) {
+	    rb_yield(rb_ary_new3(1, RARRAY_AREF(ary, i)));
+	}
+    }
+    else if (len == 0) {
+	/* yield nothing */
+    }
+    else {
+	volatile VALUE t0;
+	long *p = ALLOCV_N(long, t0, n);
+	VALUE ary0 = ary_make_shared_copy(ary); /* private defensive copy of ary */
+	RBASIC_CLEAR_CLASS(ary0);
+
+	rcombinate0(len, n, p, n, ary0); /* compute and yield repeated combinations */
+	ALLOCV_END(t0);
+	RBASIC_SET_CLASS_RAW(ary0, rb_cArray);
+    }
+    return ary;
+}
+
+/*
+ *  call-seq:
+ *     ary.product(other_ary, ...)                -> new_ary
+ *     ary.product(other_ary, ...) { |p| block }  -> ary
+ *
+ *  Returns an array of all combinations of elements from all arrays.
+ *
+ *  The length of the returned array is the product of the length of +self+ and
+ *  the argument arrays.
+ *
+ *  If given a block, #product will yield all combinations and return +self+
+ *  instead.
+ *
+ *     [1,2,3].product([4,5])     #=> [[1,4],[1,5],[2,4],[2,5],[3,4],[3,5]]
+ *     [1,2].product([1,2])       #=> [[1,1],[1,2],[2,1],[2,2]]
+ *     [1,2].product([3,4],[5,6]) #=> [[1,3,5],[1,3,6],[1,4,5],[1,4,6],
+ *                                #     [2,3,5],[2,3,6],[2,4,5],[2,4,6]]
+ *     [1,2].product()            #=> [[1],[2]]
+ *     [1,2].product([])          #=> []
+ */
+
+static VALUE
+rb_ary_product(int argc, VALUE *argv, VALUE ary)
+{
+    int n = argc+1;    /* How many arrays we're operating on */
+    volatile VALUE t0 = tmpary(n);
+    volatile VALUE t1 = tmpbuf(n, sizeof(int));
+    VALUE *arrays = RARRAY_PTR(t0); /* The arrays we're computing the product of */
+    int *counters = (int*)RSTRING_PTR(t1); /* The current position in each one */
+    VALUE result = Qnil;      /* The array we'll be returning, when no block given */
+    long i,j;
+    long resultlen = 1;
+
+    RBASIC_CLEAR_CLASS(t0);
+    RBASIC_CLEAR_CLASS(t1);
+
+    /* initialize the arrays of arrays */
+    ARY_SET_LEN(t0, n);
+    arrays[0] = ary;
+    for (i = 1; i < n; i++) arrays[i] = Qnil;
+    for (i = 1; i < n; i++) arrays[i] = to_ary(argv[i-1]);
+
+    /* initialize the counters for the arrays */
+    for (i = 0; i < n; i++) counters[i] = 0;
+
+    /* Otherwise, allocate and fill in an array of results */
+    if (rb_block_given_p()) {
+	/* Make defensive copies of arrays; exit if any is empty */
+	for (i = 0; i < n; i++) {
+	    if (RARRAY_LEN(arrays[i]) == 0) goto done;
+	    arrays[i] = ary_make_shared_copy(arrays[i]);
+	}
+    }
+    else {
+	/* Compute the length of the result array; return [] if any is empty */
+	for (i = 0; i < n; i++) {
+	    long k = RARRAY_LEN(arrays[i]);
+	    if (k == 0) {
+		result = rb_ary_new2(0);
+		goto done;
+	    }
+            if (MUL_OVERFLOW_LONG_P(resultlen, k))
+		rb_raise(rb_eRangeError, "too big to product");
+	    resultlen *= k;
+	}
+	result = rb_ary_new2(resultlen);
+    }
+    for (;;) {
+	int m;
+	/* fill in one subarray */
+	VALUE subarray = rb_ary_new2(n);
+	for (j = 0; j < n; j++) {
+	    rb_ary_push(subarray, rb_ary_entry(arrays[j], counters[j]));
+	}
+
+	/* put it on the result array */
+	if (NIL_P(result)) {
+	    FL_SET(t0, FL_USER5);
+	    rb_yield(subarray);
+	    if (! FL_TEST(t0, FL_USER5)) {
+		rb_raise(rb_eRuntimeError, "product reentered");
+	    }
+	    else {
+		FL_UNSET(t0, FL_USER5);
+	    }
+	}
+	else {
+	    rb_ary_push(result, subarray);
+	}
+
+	/*
+	 * Increment the last counter.  If it overflows, reset to 0
+	 * and increment the one before it.
+	 */
+	m = n-1;
+	counters[m]++;
+	while (counters[m] == RARRAY_LEN(arrays[m])) {
+	    counters[m] = 0;
+	    /* If the first counter overflows, we are done */
+	    if (--m < 0) goto done;
+	    counters[m]++;
+	}
+    }
+done:
+    tmpary_discard(t0);
+    tmpbuf_discard(t1);
+
+    return NIL_P(result) ? ary : result;
+}
+
+/*
+ *  call-seq:
+ *     ary.take(n)               -> new_ary
+ *
+ *  Returns first +n+ elements from the array.
+ *
+ *  If a negative number is given, raises an ArgumentError.
+ *
+ *  See also Array#drop
+ *
+ *     a = [1, 2, 3, 4, 5, 0]
+ *     a.take(3)             #=> [1, 2, 3]
+ *
+ */
+
+static VALUE
+rb_ary_take(VALUE obj, VALUE n)
+{
+    long len = NUM2LONG(n);
+    if (len < 0) {
+	rb_raise(rb_eArgError, "attempt to take negative size");
+    }
+    return rb_ary_subseq(obj, 0, len);
+}
+
+/*
+ *  call-seq:
+ *     ary.take_while { |arr| block }  -> new_ary
+ *     ary.take_while                  -> Enumerator
+ *
+ *  Passes elements to the block until the block returns +nil+ or +false+, then
+ *  stops iterating and returns an array of all prior elements.
+ *
+ *  If no block is given, an Enumerator is returned instead.
+ *
+ *  See also Array#drop_while
+ *
+ *     a = [1, 2, 3, 4, 5, 0]
+ *     a.take_while { |i| i < 3 }  #=> [1, 2]
+ *
+ */
+
+static VALUE
+rb_ary_take_while(VALUE ary)
+{
+    long i;
+
+    RETURN_ENUMERATOR(ary, 0, 0);
+    for (i = 0; i < RARRAY_LEN(ary); i++) {
+	if (!RTEST(rb_yield(RARRAY_AREF(ary, i)))) break;
+    }
+    return rb_ary_take(ary, LONG2FIX(i));
+}
+
+/*
+ *  call-seq:
+ *     ary.drop(n)               -> new_ary
+ *
+ *  Drops first +n+ elements from +ary+ and returns the rest of the elements in
+ *  an array.
+ *
+ *  If a negative number is given, raises an ArgumentError.
+ *
+ *  See also Array#take
+ *
+ *     a = [1, 2, 3, 4, 5, 0]
+ *     a.drop(3)             #=> [4, 5, 0]
+ *
+ */
+
+static VALUE
+rb_ary_drop(VALUE ary, VALUE n)
+{
+    VALUE result;
+    long pos = NUM2LONG(n);
+    if (pos < 0) {
+	rb_raise(rb_eArgError, "attempt to drop negative size");
+    }
+
+    result = rb_ary_subseq(ary, pos, RARRAY_LEN(ary));
+    if (result == Qnil) result = rb_ary_new();
+    return result;
+}
+
+/*
+ *  call-seq:
+ *     ary.drop_while { |arr| block }   -> new_ary
+ *     ary.drop_while                  -> Enumerator
+ *
+ *  Drops elements up to, but not including, the first element for which the
+ *  block returns +nil+ or +false+ and returns an array containing the
+ *  remaining elements.
+ *
+ *  If no block is given, an Enumerator is returned instead.
+ *
+ *  See also Array#take_while
+ *
+ *     a = [1, 2, 3, 4, 5, 0]
+ *     a.drop_while {|i| i < 3 }   #=> [3, 4, 5, 0]
+ *
+ */
+
+static VALUE
+rb_ary_drop_while(VALUE ary)
+{
+    long i;
+
+    RETURN_ENUMERATOR(ary, 0, 0);
+    for (i = 0; i < RARRAY_LEN(ary); i++) {
+	if (!RTEST(rb_yield(RARRAY_AREF(ary, i)))) break;
+    }
+    return rb_ary_drop(ary, LONG2FIX(i));
+}
+
+/*
+ *  call-seq:
+ *     ary.any? [{ |obj| block }]   -> true or false
+ *
+ *  See also Enumerable#any?
+ */
+
+static VALUE
+rb_ary_any_p(VALUE ary)
+{
+    long i, len = RARRAY_LEN(ary);
+    const VALUE *ptr = RARRAY_CONST_PTR(ary);
+
+    if (!len) return Qfalse;
+    if (!rb_block_given_p()) {
+	for (i = 0; i < len; ++i) if (RTEST(ptr[i])) return Qtrue;
+    }
+    else {
+	for (i = 0; i < RARRAY_LEN(ary); ++i) {
+	    if (RTEST(rb_yield(RARRAY_AREF(ary, i)))) return Qtrue;
+	}
+    }
+    return Qfalse;
+}
+
+/*
+ *  Arrays are ordered, integer-indexed collections of any object.
+ *
+ *  Array indexing starts at 0, as in C or Java.  A negative index is assumed
+ *  to be relative to the end of the array---that is, an index of -1 indicates
+ *  the last element of the array, -2 is the next to last element in the
+ *  array, and so on.
+ *
+ *  == Creating Arrays
+ *
+ *  A new array can be created by using the literal constructor
+ *  <code>[]</code>.  Arrays can contain different types of objects.  For
+ *  example, the array below contains an Integer, a String and a Float:
+ *
+ *     ary = [1, "two", 3.0] #=> [1, "two", 3.0]
+ *
+ *  An array can also be created by explicitly calling Array.new with zero, one
+ *  (the initial size of the Array) or two arguments (the initial size and a
+ *  default object).
+ *
+ *     ary = Array.new    #=> []
+ *     Array.new(3)       #=> [nil, nil, nil]
+ *     Array.new(3, true) #=> [true, true, true]
+ *
+ *  Note that the second argument populates the array with references to the
+ *  same object.  Therefore, it is only recommended in cases when you need to
+ *  instantiate arrays with natively immutable objects such as Symbols,
+ *  numbers, true or false.
+ *
+ *  To create an array with separate objects a block can be passed instead.
+ *  This method is safe to use with mutable objects such as hashes, strings or
+ *  other arrays:
+ *
+ *     Array.new(4) { Hash.new } #=> [{}, {}, {}, {}]
+ *
+ *  This is also a quick way to build up multi-dimensional arrays:
+ *
+ *     empty_table = Array.new(3) { Array.new(3) }
+ *     #=> [[nil, nil, nil], [nil, nil, nil], [nil, nil, nil]]
+ *
+ *  An array can also be created by using the Array() method, provided by
+ *  Kernel, which tries to call #to_ary, then #to_a on its argument.
+ *
+ *	Array({:a => "a", :b => "b"}) #=> [[:a, "a"], [:b, "b"]]
+ *
+ *  == Example Usage
+ *
+ *  In addition to the methods it mixes in through the Enumerable module, the
+ *  Array class has proprietary methods for accessing, searching and otherwise
+ *  manipulating arrays.
+ *
+ *  Some of the more common ones are illustrated below.
+ *
+ *  == Accessing Elements
+ *
+ *  Elements in an array can be retrieved using the Array#[] method.  It can
+ *  take a single integer argument (a numeric index), a pair of arguments
+ *  (start and length) or a range. Negative indices start counting from the end,
+ *  with -1 being the last element.
+ *
+ *     arr = [1, 2, 3, 4, 5, 6]
+ *     arr[2]    #=> 3
+ *     arr[100]  #=> nil
+ *     arr[-3]   #=> 4
+ *     arr[2, 3] #=> [3, 4, 5]
+ *     arr[1..4] #=> [2, 3, 4, 5]
+ *     arr[1..-3] #=> [2, 3, 4]
+ *
+ *  Another way to access a particular array element is by using the #at method
+ *
+ *     arr.at(0) #=> 1
+ *
+ *  The #slice method works in an identical manner to Array#[].
+ *
+ *  To raise an error for indices outside of the array bounds or else to
+ *  provide a default value when that happens, you can use #fetch.
+ *
+ *     arr = ['a', 'b', 'c', 'd', 'e', 'f']
+ *     arr.fetch(100) #=> IndexError: index 100 outside of array bounds: -6...6
+ *     arr.fetch(100, "oops") #=> "oops"
+ *
+ *  The special methods #first and #last will return the first and last
+ *  elements of an array, respectively.
+ *
+ *     arr.first #=> 1
+ *     arr.last  #=> 6
+ *
+ *  To return the first +n+ elements of an array, use #take
+ *
+ *     arr.take(3) #=> [1, 2, 3]
+ *
+ *  #drop does the opposite of #take, by returning the elements after +n+
+ *  elements have been dropped:
+ *
+ *     arr.drop(3) #=> [4, 5, 6]
+ *
+ *  == Obtaining Information about an Array
+ *
+ *  Arrays keep track of their own length at all times.  To query an array
+ *  about the number of elements it contains, use #length, #count or #size.
+ *
+ *    browsers = ['Chrome', 'Firefox', 'Safari', 'Opera', 'IE']
+ *    browsers.length #=> 5
+ *    browsers.count #=> 5
+ *
+ *  To check whether an array contains any elements at all
+ *
+ *    browsers.empty? #=> false
+ *
+ *  To check whether a particular item is included in the array
+ *
+ *    browsers.include?('Konqueror') #=> false
+ *
+ *  == Adding Items to Arrays
+ *
+ *  Items can be added to the end of an array by using either #push or #<<
+ *
+ *    arr = [1, 2, 3, 4]
+ *    arr.push(5) #=> [1, 2, 3, 4, 5]
+ *    arr << 6    #=> [1, 2, 3, 4, 5, 6]
+ *
+ *  #unshift will add a new item to the beginning of an array.
+ *
+ *     arr.unshift(0) #=> [0, 1, 2, 3, 4, 5, 6]
+ *
+ *  With #insert you can add a new element to an array at any position.
+ *
+ *     arr.insert(3, 'apple')  #=> [0, 1, 2, 'apple', 3, 4, 5, 6]
+ *
+ *  Using the #insert method, you can also insert multiple values at once:
+ *
+ *     arr.insert(3, 'orange', 'pear', 'grapefruit')
+ *     #=> [0, 1, 2, "orange", "pear", "grapefruit", "apple", 3, 4, 5, 6]
+ *
+ *  == Removing Items from an Array
+ *
+ *  The method #pop removes the last element in an array and returns it:
+ *
+ *     arr =  [1, 2, 3, 4, 5, 6]
+ *     arr.pop #=> 6
+ *     arr #=> [1, 2, 3, 4, 5]
+ *
+ *  To retrieve and at the same time remove the first item, use #shift:
+ *
+ *     arr.shift #=> 1
+ *     arr #=> [2, 3, 4, 5]
+ *
+ *  To delete an element at a particular index:
+ *
+ *     arr.delete_at(2) #=> 4
+ *     arr #=> [2, 3, 5]
+ *
+ *  To delete a particular element anywhere in an array, use #delete:
+ *
+ *     arr = [1, 2, 2, 3]
+ *     arr.delete(2) #=> 2
+ *     arr #=> [1,3]
+ *
+ *  A useful method if you need to remove +nil+ values from an array is
+ *  #compact:
+ *
+ *     arr = ['foo', 0, nil, 'bar', 7, 'baz', nil]
+ *     arr.compact  #=> ['foo', 0, 'bar', 7, 'baz']
+ *     arr          #=> ['foo', 0, nil, 'bar', 7, 'baz', nil]
+ *     arr.compact! #=> ['foo', 0, 'bar', 7, 'baz']
+ *     arr          #=> ['foo', 0, 'bar', 7, 'baz']
+ *
+ *  Another common need is to remove duplicate elements from an array.
+ *
+ *  It has the non-destructive #uniq, and destructive method #uniq!
+ *
+ *     arr = [2, 5, 6, 556, 6, 6, 8, 9, 0, 123, 556]
+ *     arr.uniq #=> [2, 5, 6, 556, 8, 9, 0, 123]
+ *
+ *  == Iterating over Arrays
+ *
+ *  Like all classes that include the Enumerable module, Array has an each
+ *  method, which defines what elements should be iterated over and how.  In
+ *  case of Array's #each, all elements in the Array instance are yielded to
+ *  the supplied block in sequence.
+ *
+ *  Note that this operation leaves the array unchanged.
+ *
+ *     arr = [1, 2, 3, 4, 5]
+ *     arr.each { |a| print a -= 10, " " }
+ *     # prints: -9 -8 -7 -6 -5
+ *     #=> [1, 2, 3, 4, 5]
+ *
+ *  Another sometimes useful iterator is #reverse_each which will iterate over
+ *  the elements in the array in reverse order.
+ *
+ *     words = %w[first second third fourth fifth sixth]
+ *     str = ""
+ *     words.reverse_each { |word| str += "#{word} " }
+ *     p str #=> "sixth fifth fourth third second first "
+ *
+ *  The #map method can be used to create a new array based on the original
+ *  array, but with the values modified by the supplied block:
+ *
+ *     arr.map { |a| 2*a }   #=> [2, 4, 6, 8, 10]
+ *     arr                   #=> [1, 2, 3, 4, 5]
+ *     arr.map! { |a| a**2 } #=> [1, 4, 9, 16, 25]
+ *     arr                   #=> [1, 4, 9, 16, 25]
+ *
+ *  == Selecting Items from an Array
+ *
+ *  Elements can be selected from an array according to criteria defined in a
+ *  block.  The selection can happen in a destructive or a non-destructive
+ *  manner.  While the destructive operations will modify the array they were
+ *  called on, the non-destructive methods usually return a new array with the
+ *  selected elements, but leave the original array unchanged.
+ *
+ *  === Non-destructive Selection
+ *
+ *     arr = [1, 2, 3, 4, 5, 6]
+ *     arr.select { |a| a > 3 }     #=> [4, 5, 6]
+ *     arr.reject { |a| a < 3 }     #=> [3, 4, 5, 6]
+ *     arr.drop_while { |a| a < 4 } #=> [4, 5, 6]
+ *     arr                          #=> [1, 2, 3, 4, 5, 6]
+ *
+ *  === Destructive Selection
+ *
+ *  #select! and #reject! are the corresponding destructive methods to #select
+ *  and #reject
+ *
+ *  Similar to #select vs. #reject, #delete_if and #keep_if have the exact
+ *  opposite result when supplied with the same block:
+ *
+ *     arr.delete_if { |a| a < 4 } #=> [4, 5, 6]
+ *     arr                         #=> [4, 5, 6]
+ *
+ *     arr = [1, 2, 3, 4, 5, 6]
+ *     arr.keep_if { |a| a < 4 } #=> [1, 2, 3]
+ *     arr                       #=> [1, 2, 3]
+ *
+ */
+
+void
+Init_Array(void)
+{
+#undef rb_intern
+#define rb_intern(str) rb_intern_const(str)
+
+    rb_cArray  = rb_define_class("Array", rb_cObject);
+    rb_include_module(rb_cArray, rb_mEnumerable);
+
+    rb_define_alloc_func(rb_cArray, empty_ary_alloc);
+    rb_define_singleton_method(rb_cArray, "[]", rb_ary_s_create, -1);
+    rb_define_singleton_method(rb_cArray, "try_convert", rb_ary_s_try_convert, 1);
+    rb_define_method(rb_cArray, "initialize", rb_ary_initialize, -1);
+    rb_define_method(rb_cArray, "initialize_copy", rb_ary_replace, 1);
+
+    rb_define_method(rb_cArray, "inspect", rb_ary_inspect, 0);
+    rb_define_alias(rb_cArray,  "to_s", "inspect");
+    rb_define_method(rb_cArray, "to_a", rb_ary_to_a, 0);
+    rb_define_method(rb_cArray, "to_h", rb_ary_to_h, 0);
+    rb_define_method(rb_cArray, "to_ary", rb_ary_to_ary_m, 0);
+    rb_define_method(rb_cArray, "frozen?",  rb_ary_frozen_p, 0);
+
+    rb_define_method(rb_cArray, "==", rb_ary_equal, 1);
+    rb_define_method(rb_cArray, "eql?", rb_ary_eql, 1);
+    rb_define_method(rb_cArray, "hash", rb_ary_hash, 0);
+
+    rb_define_method(rb_cArray, "[]", rb_ary_aref, -1);
+    rb_define_method(rb_cArray, "[]=", rb_ary_aset, -1);
+    rb_define_method(rb_cArray, "at", rb_ary_at, 1);
+    rb_define_method(rb_cArray, "fetch", rb_ary_fetch, -1);
+    rb_define_method(rb_cArray, "first", rb_ary_first, -1);
+    rb_define_method(rb_cArray, "last", rb_ary_last, -1);
+    rb_define_method(rb_cArray, "concat", rb_ary_concat, 1);
+    rb_define_method(rb_cArray, "<<", rb_ary_push, 1);
+    rb_define_method(rb_cArray, "push", rb_ary_push_m, -1);
+    rb_define_method(rb_cArray, "pop", rb_ary_pop_m, -1);
+    rb_define_method(rb_cArray, "shift", rb_ary_shift_m, -1);
+    rb_define_method(rb_cArray, "unshift", rb_ary_unshift_m, -1);
+    rb_define_method(rb_cArray, "insert", rb_ary_insert, -1);
+    rb_define_method(rb_cArray, "each", rb_ary_each, 0);
+    rb_define_method(rb_cArray, "each_index", rb_ary_each_index, 0);
+    rb_define_method(rb_cArray, "reverse_each", rb_ary_reverse_each, 0);
+    rb_define_method(rb_cArray, "length", rb_ary_length, 0);
+    rb_define_alias(rb_cArray,  "size", "length");
+    rb_define_method(rb_cArray, "empty?", rb_ary_empty_p, 0);
+    rb_define_method(rb_cArray, "find_index", rb_ary_index, -1);
+    rb_define_method(rb_cArray, "index", rb_ary_index, -1);
+    rb_define_method(rb_cArray, "rindex", rb_ary_rindex, -1);
+    rb_define_method(rb_cArray, "join", rb_ary_join_m, -1);
+    rb_define_method(rb_cArray, "reverse", rb_ary_reverse_m, 0);
+    rb_define_method(rb_cArray, "reverse!", rb_ary_reverse_bang, 0);
+    rb_define_method(rb_cArray, "rotate", rb_ary_rotate_m, -1);
+    rb_define_method(rb_cArray, "rotate!", rb_ary_rotate_bang, -1);
+    rb_define_method(rb_cArray, "sort", rb_ary_sort, 0);
+    rb_define_method(rb_cArray, "sort!", rb_ary_sort_bang, 0);
+    rb_define_method(rb_cArray, "sort_by!", rb_ary_sort_by_bang, 0);
+    rb_define_method(rb_cArray, "collect", rb_ary_collect, 0);
+    rb_define_method(rb_cArray, "collect!", rb_ary_collect_bang, 0);
+    rb_define_method(rb_cArray, "map", rb_ary_collect, 0);
+    rb_define_method(rb_cArray, "map!", rb_ary_collect_bang, 0);
+    rb_define_method(rb_cArray, "select", rb_ary_select, 0);
+    rb_define_method(rb_cArray, "select!", rb_ary_select_bang, 0);
+    rb_define_method(rb_cArray, "keep_if", rb_ary_keep_if, 0);
+    rb_define_method(rb_cArray, "values_at", rb_ary_values_at, -1);
+    rb_define_method(rb_cArray, "delete", rb_ary_delete, 1);
+    rb_define_method(rb_cArray, "delete_at", rb_ary_delete_at_m, 1);
+    rb_define_method(rb_cArray, "delete_if", rb_ary_delete_if, 0);
+    rb_define_method(rb_cArray, "reject", rb_ary_reject, 0);
+    rb_define_method(rb_cArray, "reject!", rb_ary_reject_bang, 0);
+    rb_define_method(rb_cArray, "zip", rb_ary_zip, -1);
+    rb_define_method(rb_cArray, "transpose", rb_ary_transpose, 0);
+    rb_define_method(rb_cArray, "replace", rb_ary_replace, 1);
+    rb_define_method(rb_cArray, "clear", rb_ary_clear, 0);
+    rb_define_method(rb_cArray, "fill", rb_ary_fill, -1);
+    rb_define_method(rb_cArray, "include?", rb_ary_includes, 1);
+    rb_define_method(rb_cArray, "<=>", rb_ary_cmp, 1);
+
+    rb_define_method(rb_cArray, "slice", rb_ary_aref, -1);
+    rb_define_method(rb_cArray, "slice!", rb_ary_slice_bang, -1);
+
+    rb_define_method(rb_cArray, "assoc", rb_ary_assoc, 1);
+    rb_define_method(rb_cArray, "rassoc", rb_ary_rassoc, 1);
+
+    rb_define_method(rb_cArray, "+", rb_ary_plus, 1);
+    rb_define_method(rb_cArray, "*", rb_ary_times, 1);
+
+    rb_define_method(rb_cArray, "-", rb_ary_diff, 1);
+    rb_define_method(rb_cArray, "&", rb_ary_and, 1);
+    rb_define_method(rb_cArray, "|", rb_ary_or, 1);
+
+    rb_define_method(rb_cArray, "uniq", rb_ary_uniq, 0);
+    rb_define_method(rb_cArray, "uniq!", rb_ary_uniq_bang, 0);
+    rb_define_method(rb_cArray, "compact", rb_ary_compact, 0);
+    rb_define_method(rb_cArray, "compact!", rb_ary_compact_bang, 0);
+    rb_define_method(rb_cArray, "flatten", rb_ary_flatten, -1);
+    rb_define_method(rb_cArray, "flatten!", rb_ary_flatten_bang, -1);
+    rb_define_method(rb_cArray, "count", rb_ary_count, -1);
+    rb_define_method(rb_cArray, "shuffle!", rb_ary_shuffle_bang, -1);
+    rb_define_method(rb_cArray, "shuffle", rb_ary_shuffle, -1);
+    rb_define_method(rb_cArray, "sample", rb_ary_sample, -1);
+    rb_define_method(rb_cArray, "cycle", rb_ary_cycle, -1);
+    rb_define_method(rb_cArray, "permutation", rb_ary_permutation, -1);
+    rb_define_method(rb_cArray, "combination", rb_ary_combination, 1);
+    rb_define_method(rb_cArray, "repeated_permutation", rb_ary_repeated_permutation, 1);
+    rb_define_method(rb_cArray, "repeated_combination", rb_ary_repeated_combination, 1);
+    rb_define_method(rb_cArray, "product", rb_ary_product, -1);
+
+    rb_define_method(rb_cArray, "take", rb_ary_take, 1);
+    rb_define_method(rb_cArray, "take_while", rb_ary_take_while, 0);
+    rb_define_method(rb_cArray, "drop", rb_ary_drop, 1);
+    rb_define_method(rb_cArray, "drop_while", rb_ary_drop_while, 0);
+    rb_define_method(rb_cArray, "bsearch", rb_ary_bsearch, 0);
+    rb_define_method(rb_cArray, "any?", rb_ary_any_p, 0);
+
+    id_cmp = rb_intern("<=>");
+    id_random = rb_intern("random");
+    id_div = rb_intern("div");
+    id_power = rb_intern("**");
+}