Array には <=> も == も定義されているのに Comparable を include
していないようですが、何か理由がありましたっけ?

knu@archon[2]% irb
irb(main):001:0> [1,2] <=> [1,3]
-1
irb(main):002:0> [1,2] == [1,3]
false
irb(main):003:0> [1,2] < [1,3]
NameError: undefined method `<' for [1, 2]:Array
	from (irb):3

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Akinori MUSHA aka / (_ /  ( (__(  @ iDaemons.org / and.or.jp

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Index: array.c
===================================================================
RCS file: /src/ruby/array.c,v
retrieving revision 1.57
diff -u -p -r1.57 array.c
--- array.c	2001/08/29 06:28:44	1.57
+++ array.c	2001/09/16 05:23:56
@@ -1700,6 +1700,7 @@ void
 Init_Array()
 {
     rb_cArray  = rb_define_class("Array", rb_cObject);
+    rb_include_module(rb_cArray, rb_mComparable);
     rb_include_module(rb_cArray, rb_mEnumerable);
 
     rb_define_singleton_method(rb_cArray, "new", rb_ary_s_new, -1);