From: nobu.nokada@...
Date: 2004-05-26T05:24:59+09:00
Subject: Re: [RCR] Enumerable#group_by

Hi,

At Wed, 26 May 2004 02:16:27 +0900,
Michael Neumann wrote in [ruby-talk:101382]:
> I propose the addition of Enumerable#group_by which is a generalization
> of Enumerable#partition.

I think it has been proposed also as Enumerable#classify.  Here
is a patch I made at that time.


Index: enum.c
===================================================================
RCS file: /cvs/ruby/src/ruby/enum.c,v
retrieving revision 1.45
diff -U2 -p -d -r1.45 enum.c
--- enum.c	14 Apr 2004 04:06:24 -0000	1.45
+++ enum.c	21 Apr 2004 08:37:31 -0000
@@ -362,4 +362,37 @@ enum_partition(obj)
 }
 
+static VALUE
+classify_i(i, hash)
+    VALUE i, hash;
+{
+    VALUE k = rb_yield(i);
+    VALUE ary = rb_hash_aref(hash, k);
+
+    if (NIL_P(ary)) {
+	rb_hash_aset(hash, k, ary = rb_ary_new());
+    }
+    rb_ary_push(ary, i);
+
+    return Qnil;
+}
+
+/*
+ *  call-seq:
+ *     enum.classify {| x | block }  => hash
+ *
+ *  Returns a hash containing the items in <i>enum</i> classified.
+ */
+
+static VALUE
+enum_classify(obj)
+    VALUE obj;
+{
+    VALUE hash = rb_hash_new();
+
+    rb_iterate(rb_each, obj, classify_i, hash);
+
+    return hash;
+}
+
 /*
  *  call-seq:
@@ -930,4 +963,5 @@ Init_Enumerable()
     rb_define_method(rb_mEnumerable,"inject", enum_inject, -1);
     rb_define_method(rb_mEnumerable,"partition", enum_partition, 0);
+    rb_define_method(rb_mEnumerable,"classify", enum_classify, 0);
     rb_define_method(rb_mEnumerable,"all?", enum_all, 0);
     rb_define_method(rb_mEnumerable,"any?", enum_any, 0);


-- 
Nobu Nakada