https://git.ruby-lang.org/ruby.git/commit/?id=1a73a6cdd2

From 1a73a6cdd2068b815430b775fe25186dab693faa Mon Sep 17 00:00:00 2001
From: Akinori MUSHA <knu@i...>
Date: Fri, 29 Jul 2022 13:56:54 +0900
Subject: Implement Enumerator::Product and Enumerator.product [Feature #18685]

---
 enumerator.c                 | 354 ++++++++++++++++++++++++++++++++++++++++++-
 test/ruby/test_enumerator.rb |  38 +++++
 2 files changed, 391 insertions(+), 1 deletion(-)

diff --git a/enumerator.c b/enumerator.c
index 89abf4b888..ce2eacbd2a 100644
--- a/enumerator.c
+++ b/enumerator.c
@@ -125,7 +125,7 @@ https://github.com/ruby/ruby/blob/trunk/enumerator.c#L125
  */
 VALUE rb_cEnumerator;
 static VALUE rb_cLazy;
-static ID id_rewind, id_new, id_to_enum;
+static ID id_rewind, id_new, id_to_enum, id_each_entry;
 static ID id_next, id_result, id_receiver, id_arguments, id_memo, id_method, id_force;
 static ID id_begin, id_end, id_step, id_exclude_end;
 static VALUE sym_each, sym_cycle, sym_yield;
@@ -194,6 +194,12 @@ struct enum_chain { https://github.com/ruby/ruby/blob/trunk/enumerator.c#L194
     long pos;
 };
 
+static VALUE rb_cEnumProduct;
+
+struct enum_product {
+    VALUE enums;
+};
+
 VALUE rb_cArithSeq;
 
 /*
@@ -3347,6 +3353,335 @@ enumerator_plus(VALUE obj, VALUE eobj) https://github.com/ruby/ruby/blob/trunk/enumerator.c#L3353
     return new_enum_chain(rb_ary_new_from_args(2, obj, eobj));
 }
 
+/*
+ * Document-class: Enumerator::Product
+ *
+ * Enumerator::Product generates a Cartesian product of any number of
+ * enumerable objects.  Iterating over the product of enumerable
+ * objects is roughly equivalent to nested each_entry loops where the
+ * loop for the rightmost object is put innermost.
+ *
+ *   innings = Enumerator::Product.new(1..9, ['top', 'bottom'])
+ *
+ *   innings.each do |i, h|
+ *     p [i, h]
+ *   end
+ *   # [1, "top"]
+ *   # [1, "bottom"]
+ *   # [2, "top"]
+ *   # [2, "bottom"]
+ *   # [3, "top"]
+ *   # [3, "bottom"]
+ *   # ...
+ *   # [9, "top"]
+ *   # [9, "bottom"]
+ *
+ * The method used against each enumerable object is `each_entry`
+ * instead of `each` so that the product of N enumerable objects
+ * yields exactly N arguments in each iteration.
+ *
+ * When no enumerator is given, it calls a given block once yielding
+ * an empty argument list.
+ *
+ * This type of objects can be created by Enumerator.product.
+ */
+
+static void
+enum_product_mark(void *p)
+{
+    struct enum_product *ptr = p;
+    rb_gc_mark_movable(ptr->enums);
+}
+
+static void
+enum_product_compact(void *p)
+{
+    struct enum_product *ptr = p;
+    ptr->enums = rb_gc_location(ptr->enums);
+}
+
+#define enum_product_free RUBY_TYPED_DEFAULT_FREE
+
+static size_t
+enum_product_memsize(const void *p)
+{
+    return sizeof(struct enum_product);
+}
+
+static const rb_data_type_t enum_product_data_type = {
+    "product",
+    {
+        enum_product_mark,
+        enum_product_free,
+        enum_product_memsize,
+        enum_product_compact,
+    },
+    0, 0, RUBY_TYPED_FREE_IMMEDIATELY
+};
+
+static struct enum_product *
+enum_product_ptr(VALUE obj)
+{
+    struct enum_product *ptr;
+
+    TypedData_Get_Struct(obj, struct enum_product, &enum_product_data_type, ptr);
+    if (!ptr || ptr->enums == Qundef) {
+        rb_raise(rb_eArgError, "uninitialized product");
+    }
+    return ptr;
+}
+
+/* :nodoc: */
+static VALUE
+enum_product_allocate(VALUE klass)
+{
+    struct enum_product *ptr;
+    VALUE obj;
+
+    obj = TypedData_Make_Struct(klass, struct enum_product, &enum_product_data_type, ptr);
+    ptr->enums = Qundef;
+
+    return obj;
+}
+
+/*
+ * call-seq:
+ *   Enumerator::Product.new(*enums) -> enum
+ *
+ * Generates a new enumerator object that generates a Cartesian
+ * product of given enumerable objects.
+ *
+ *   e = Enumerator::Product.new(1..3, [4, 5])
+ *   e.to_a #=> [[1, 4], [1, 5], [2, 4], [2, 5], [3, 4], [3, 5]]
+ *   e.size #=> 6
+ */
+static VALUE
+enum_product_initialize(VALUE obj, VALUE enums)
+{
+    struct enum_product *ptr;
+
+    rb_check_frozen(obj);
+    TypedData_Get_Struct(obj, struct enum_product, &enum_product_data_type, ptr);
+
+    if (!ptr) rb_raise(rb_eArgError, "unallocated product");
+
+    ptr->enums = rb_obj_freeze(enums);
+
+    return obj;
+}
+
+/* :nodoc: */
+static VALUE
+enum_product_init_copy(VALUE obj, VALUE orig)
+{
+    struct enum_product *ptr0, *ptr1;
+
+    if (!OBJ_INIT_COPY(obj, orig)) return obj;
+    ptr0 = enum_product_ptr(orig);
+
+    TypedData_Get_Struct(obj, struct enum_product, &enum_product_data_type, ptr1);
+
+    if (!ptr1) rb_raise(rb_eArgError, "unallocated product");
+
+    ptr1->enums = ptr0->enums;
+
+    return obj;
+}
+
+static VALUE
+enum_product_total_size(VALUE enums)
+{
+    VALUE total = INT2FIX(1);
+    long i;
+
+    for (i = 0; i < RARRAY_LEN(enums); i++) {
+        VALUE size = enum_size(RARRAY_AREF(enums, i));
+
+        if (NIL_P(size) || (RB_TYPE_P(size, T_FLOAT) && isinf(NUM2DBL(size)))) {
+            return size;
+        }
+        if (!RB_INTEGER_TYPE_P(size)) {
+            return Qnil;
+        }
+
+        total = rb_funcall(total, '*', 1, size);
+    }
+
+    return total;
+}
+
+/*
+ * call-seq:
+ *   obj.size -> int, Float::INFINITY or nil
+ *
+ * Returns the total size of the enumerator product calculated by
+ * multiplying the sizes of enumerables in the product.  If any of the
+ * enumerables reports its size as nil or Float::INFINITY, that value
+ * is returned as the size.
+ */
+static VALUE
+enum_product_size(VALUE obj)
+{
+    return enum_product_total_size(enum_product_ptr(obj)->enums);
+}
+
+static VALUE
+enum_product_enum_size(VALUE obj, VALUE args, VALUE eobj)
+{
+    return enum_product_size(obj);
+}
+
+struct product_state {
+    VALUE  obj;
+    VALUE  block;
+    int    argc;
+    VALUE *argv;
+    int    index;
+};
+
+static VALUE product_each(VALUE, struct product_state *);
+
+static VALUE
+product_each_i(RB_BLOCK_CALL_FUNC_ARGLIST(value, state))
+{
+    struct product_state *pstate = (struct product_state *)state;
+    pstate->argv[pstate->index++] = value;
+
+    VALUE val = product_each(pstate->obj, pstate);
+    pstate->index--;
+    return val;
+}
+
+static VALUE
+product_each(VALUE obj, struct product_state *pstate)
+{
+    struct enum_product *ptr = enum_product_ptr(obj);
+    VALUE enums = ptr->enums;
+
+    if (pstate->index < pstate->argc) {
+        VALUE eobj = RARRAY_AREF(enums, pstate->index);
+
+        rb_block_call(eobj, id_each_entry, 0, NULL, product_each_i, (VALUE)pstate);
+    } else {
+        rb_funcallv(pstate->block, id_call, pstate->argc, pstate->argv);
+    }
+
+    return obj;
+}
+
+static VALUE
+enum_product_run(VALUE obj, VALUE block)
+{
+    struct enum_product *ptr = enum_product_ptr(obj);
+    int argc = RARRAY_LENINT(ptr->enums);
+    struct product_state state = {
+        .obj = obj,
+        .block = block,
+        .index = 0,
+        .argc = argc,
+        .argv = ALLOCA_N(VALUE, argc),
+    };
+
+    return product_each(obj, &state);
+}
+
+/*
+ * call-seq:
+ *   obj.each { |...| ... } -> obj
+ *   obj.each -> enumerator
+ *
+ * Iterates over the elements of the first enumerable by calling the
+ * "each_entry" method on it with the given arguments, then proceeds
+ * to the following enumerables in sequence until all of the
+ * enumerables are exhausted.
+ *
+ * If no block is given, returns an enumerator.  Otherwise, returns self.
+ */
+static VALUE
+enum_product_each(VALUE obj)
+{
+    RETURN_SIZED_ENUMERATOR(obj, 0, 0, enum_product_enum_size);
+
+    return enum_product_run(obj, rb_block_proc());
+}
+
+/*
+ * call-seq:
+ *   obj.rewind -> obj
+ *
+ * Rewinds the product enumerator by calling the "rewind" method on
+ * each enumerable in reverse order.  Each call is performed only if
+ * the enumerable responds to the method.
+ */
+static VALUE
+enum_product_rewind(VALUE obj)
+{
+    struct enum_product *ptr = enum_product_ptr(obj);
+    VALUE enums = ptr->enums;
+    long i;
+
+    for (i = 0; i < RARRAY_LEN(enums); i++) {
+        rb_check_funcall(RARRAY_AREF(enums, i), id_rewind, 0, 0);
+    }
+
+    return obj;
+}
+
+static VALUE
+inspect_enum_product(VALUE obj, VALUE dummy, int recur)
+{
+    VALUE klass = rb_obj_class(obj);
+    struct enum_product *ptr;
+
+    TypedData_Get_Struct(obj, struct enum_product, &enum_product_data_type, ptr);
+
+    if (!ptr || ptr->enums == Qundef) {
+        return rb_sprintf("#<%"PRIsVALUE": uninitialized>", rb_class_path(klass));
+    }
+
+    if (recur) {
+        return rb_sprintf("#<%"PRIsVALUE": ...>", rb_class_path(klass));
+    }
+
+    return rb_sprintf("#<%"PRIsVALUE": %+"PRIsVALUE">", rb_class_path(klass), ptr->enums);
+}
+
+/*
+ * call-seq:
+ *   obj.inspect -> string
+ *
+ * Returns a printable version of the product enumerator.
+ */
+static VALUE
+enum_product_inspect(VALUE obj)
+{
+    return rb_exec_recursive(inspect_enum_product, obj, 0);
+}
+
+/*
+ * call-seq:
+ *   Enumerator.product(*enums) -> enumerator
+ *
+ * Generates a new enumerator object that generates a Cartesian
+ * product of given enumerable objects.  This is equivalent to
+ * Enumerator::Product.new.
+ *
+ *   e = Enumerator.product(1..3, [4, 5])
+ *   e.to_a #=> [[1, 4], [1, 5], [2, 4], [2, 5], [3, 4], [3, 5]]
+ *   e.size #=> 6
+ */
+static VALUE
+enumerator_s_product(VALUE klass, VALUE enums)
+{
+    VALUE obj = enum_product_initialize(enum_product_allocate(rb_cEnumProduct), enums);
+
+    if (rb_block_given_p()) {
+        return enum_product_run(obj, rb_block_proc());
+    } else {
+        return obj;
+    }
+}
+
 /*
  * Document-class: Enumerator::ArithmeticSequence
  *
@@ -4214,6 +4549,22 @@ InitVM_Enumerator(void) https://github.com/ruby/ruby/blob/trunk/enumerator.c#L4549
     rb_undef_method(rb_cEnumChain, "peek");
     rb_undef_method(rb_cEnumChain, "peek_values");
 
+    /* Product */
+    rb_cEnumProduct = rb_define_class_under(rb_cEnumerator, "Product", rb_cEnumerator);
+    rb_define_alloc_func(rb_cEnumProduct, enum_product_allocate);
+    rb_define_method(rb_cEnumProduct, "initia (... truncated)

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