From: Akinori MUSHA <knu@...>
Date: 2008-04-11T23:55:44+09:00
Subject: [ruby-dev:34346] Enumerable.cycle(n)

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　Enumerable#cycle を回数指定可能にするのはどうでしょうか。

(1..3).cycle(2) { |obj| ... }  # 1,2,3,1,2,3

　何回目なのかを渡す #cycle_with_counter { |obj, counter| .. } も
ほしいかも。(下のパッチには含まれていません)

Index: array.c
===================================================================
--- array.c	(revision 15977)
+++ array.c	(working copy)
@@ -2938,25 +2938,41 @@
 /*
  *  call-seq:
  *     ary.cycle {|obj| block }
+ *     ary.cycle(n) {|obj| block }
  *
- *  Calls <i>block</i> repeatedly forever.
+ *  Calls <i>block</i> for each element repeatedly _n_ times or
+ *  forever if none or nil is given.  If a non-positive number is
+ *  given or the array is empty, does nothing.  Returns nil if the
+ *  loop has finished without getting interrupted.
  *
  *     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(VALUE ary)
+rb_ary_cycle(int argc, VALUE *argv, VALUE ary)
 {
-    long i;
+    long n, i;
+    VALUE nv = Qnil;

-    RETURN_ENUMERATOR(ary, 0, 0);
-    while (RARRAY_LEN(ary) > 0) {
-	for (i=0; i<RARRAY_LEN(ary); i++) {
-	    rb_yield(RARRAY_PTR(ary)[i]);
-	}
+    rb_scan_args(argc, argv, "01", &nv);
+
+    RETURN_ENUMERATOR(ary, argc, argv);
+    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_PTR(ary)[i]);
+        }
+    }
     return Qnil;
 }

@@ -3430,7 +3446,7 @@
     rb_define_method(rb_cArray, "shuffle!", rb_ary_shuffle_bang, 0);
     rb_define_method(rb_cArray, "shuffle", rb_ary_shuffle, 0);
     rb_define_method(rb_cArray, "choice", rb_ary_choice, 0);
-    rb_define_method(rb_cArray, "cycle", rb_ary_cycle, 0);
+    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, "product", rb_ary_product, -1);
Index: enum.c
===================================================================
--- enum.c	(revision 15977)
+++ enum.c	(working copy)
@@ -1656,33 +1656,48 @@
 /*
  *  call-seq:
  *     enum.cycle {|obj| block }
+ *     enum.cycle(n) {|obj| block }
  *
- *  Calls <i>block</i> for each element of <i>enum</i> repeatedly
- *  forever. Returns nil if and only if the collection is empty.
+ *  Calls <i>block</i> for each element of <i>enum</i> repeatedly _n_
+ *  times or forever if none or nil is given.  If a non-positive
+ *  number is given or the collection is empty, does nothing.  Returns
+ *  nil if the loop has finished without getting interrupted.
+ *
  *  Enumerable#cycle saves elements in an internal array so changes
  *  to <i>enum</i> after the first pass have no effect.
  *
  *     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
-enum_cycle(VALUE obj)
+enum_cycle(int argc, VALUE *argv, VALUE obj)
 {
     VALUE ary;
-    long i, len;
+    VALUE nv = Qnil;
+    long n, i, len;

-    RETURN_ENUMERATOR(obj, 0, 0);
+    rb_scan_args(argc, argv, "01", &nv);
+
+    RETURN_ENUMERATOR(obj, argc, argv);
+    if (NIL_P(nv)) {
+        n = -1;
+    }
+    else {
+        n = NUM2LONG(nv);
+        if (n <= 0) return Qnil;
+    }
     ary = rb_ary_new();
     RBASIC(ary)->klass = 0;
     rb_block_call(obj, id_each, 0, 0, cycle_i, ary);
     len = RARRAY_LEN(ary);
     if (len == 0) return Qnil;
-    for (;;) {
-	for (i=0; i<len; i++) {
-	    rb_yield(RARRAY_PTR(ary)[i]);
-	}
+    while (n < 0 || 0 < --n) {
+        for (i=0; i<len; i++) {
+            rb_yield(RARRAY_PTR(ary)[i]);
+        }
     }
     return Qnil;		/* not reached */
 }
@@ -1741,7 +1756,7 @@
     rb_define_method(rb_mEnumerable, "take_while", enum_take_while, 0);
     rb_define_method(rb_mEnumerable, "drop", enum_drop, 1);
     rb_define_method(rb_mEnumerable, "drop_while", enum_drop_while, 0);
-    rb_define_method(rb_mEnumerable, "cycle", enum_cycle, 0);
+    rb_define_method(rb_mEnumerable, "cycle", enum_cycle, -1);

     id_eqq  = rb_intern("===");
     id_each = rb_intern("each");


--
Akinori MUSHA / http://akinori.org/

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