From: Akinori MUSHA <knu@...>
Date: 2008-04-10T23:48:54+09:00
Subject: [ruby-dev:34313] Enumerable#find_index vs. Array#index

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　[ruby-talk:178495] が発端で Enumerable#find_index というのが
以前追加されましたが、機能的には Array#index のサブセットです。
(index はブロック評価、指定値との比較を両サポート)

　Array 以外では #index(value) に相当する機能がないので、
Enumerable#find_index(value) をサポートしてはどうでしょうか。
(そして Array では効率のため alias find_index index します)

Index: enum.c
===================================================================
--- enum.c	(revision 15954)
+++ enum.c	(working copy)
@@ -186,8 +186,19 @@
 }

 static VALUE
-find_index_i(VALUE i, VALUE *memo, int argc, VALUE *argv)
+find_index_i(VALUE i, VALUE *memo)
 {
+    if (rb_equal(i, memo[2])) {
+	memo[0] = UINT2NUM(memo[1]);
+	rb_iter_break();
+    }
+    memo[1]++;
+    return Qnil;
+}
+
+static VALUE
+find_index_iter_i(VALUE i, VALUE *memo, int argc, VALUE *argv)
+{
     if (RTEST(enum_yield(argc, argv))) {
 	memo[0] = UINT2NUM(memo[1]);
 	rb_iter_break();
@@ -198,30 +209,48 @@

 /*
  *  call-seq:
- *     enum.find_index()   {| obj | block }  => int
+ *     enum.find_index(value)            => int or nil
+ *     enum.find_index {| obj | block }  => int or nil
  *
- *  Passes each entry in <i>enum</i> to <em>block</em>. Returns the
- *  index for the first for which <em>block</em> is not <code>false</code>.
- *  If no object matches, returns <code>nil</code>
+ *  Compares each entry in <i>enum</i> with <em>value</em> or passes
+ *  to <em>block</em>.  Returns the index for the first for which the
+ *  evaluated value is non-false.  If no object matches, returns
+ *  <code>nil</code>
  *
  *     (1..10).find_index  {|i| i % 5 == 0 and i % 7 == 0 }   #=> nil
  *     (1..100).find_index {|i| i % 5 == 0 and i % 7 == 0 }   #=> 34
+ *     (1..100).find_index(50)                                #=> 49
  *
  */

 static VALUE
-enum_find_index(VALUE obj)
+enum_find_index(int argc, VALUE *argv, VALUE obj)
 {
-    VALUE memo[2];
+    VALUE memo[3];	/* [return value, current index, condition value] */
+    rb_block_call_func *func;

-    RETURN_ENUMERATOR(obj, 0, 0);
-    memo[0] = Qundef;
-    memo[1] = 0;
-    rb_block_call(obj, id_each, 0, 0, find_index_i, (VALUE)memo);
-    if (memo[0] != Qundef) {
-	return memo[0];
+    if (argc == 0) {
+        RETURN_ENUMERATOR(obj, 0, 0);
+        memo[0] = Qnil;
+        memo[1] = 0;
+        memo[2] = Qundef;
+        func = find_index_iter_i;
     }
-    return Qnil;
+    else {
+        VALUE item;
+
+	if (rb_block_given_p()) {
+	    rb_warn("given block not used");
+	}
+	rb_scan_args(argc, argv, "1", &item);
+        memo[0] = Qnil;
+        memo[1] = 0;
+        memo[2] = item;
+        func = find_index_i;
+    }
+
+    rb_block_call(obj, id_each, 0, 0, func, (VALUE)memo);
+    return memo[0];
 }

 static VALUE
@@ -1688,7 +1717,7 @@
     rb_define_method(rb_mEnumerable,"count", enum_count, -1);
     rb_define_method(rb_mEnumerable,"find", enum_find, -1);
     rb_define_method(rb_mEnumerable,"detect", enum_find, -1);
-    rb_define_method(rb_mEnumerable,"find_index", enum_find_index, 0);
+    rb_define_method(rb_mEnumerable,"find_index", enum_find_index, -1);
     rb_define_method(rb_mEnumerable,"find_all", enum_find_all, 0);
     rb_define_method(rb_mEnumerable,"select", enum_find_all, 0);
     rb_define_method(rb_mEnumerable,"reject", enum_reject, 0);
Index: array.c
===================================================================
--- array.c	(revision 15954)
+++ array.c	(working copy)
@@ -877,6 +877,8 @@
  *     a.index("b")        #=> 1
  *     a.index("z")        #=> nil
  *     a.index{|x|x=="b"}  #=> 1
+ *
+ *  This is an alias of <code>#find_index</code>.
  */

 static VALUE
@@ -3378,6 +3380,7 @@
     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);

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

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