From: Nobuyoshi Nakada <nobu@...>
Date: 2009-09-05T06:49:35+09:00
Subject: [ruby-core:25384] Re: [Feature #1697] Object#<=>

Hi,

At Sun, 28 Jun 2009 10:48:45 +0900,
Marc-Andre Lafortune wrote in [ruby-core:24063]:
> Other comparison operators like <, <=, >=, > would also gain
> in consistency if they were defined in terms of <=>. This
> way, 0 < nil and nil > 0 would raise the same errors instead
> of errors of different types. This is secondary to the main
> question: is it better to define Object#<=> or not?
> My vote is on 'yes'.

A patch for it.


Index: object.c
===================================================================
--- object.c	(revision 24752)
+++ object.c	(working copy)
@@ -32,5 +32,5 @@ VALUE rb_cTrueClass;
 VALUE rb_cFalseClass;
 
-static ID id_eq, id_eql, id_match, id_inspect, id_init_copy;
+static ID id_eq, id_eql, id_match, id_inspect, id_init_copy, id_cmp;
 
 /*
@@ -1116,4 +1116,14 @@ rb_obj_not_match(VALUE obj1, VALUE obj2)
 }
 
+/* :nodoc: */
+static VALUE
+rb_obj_cmp(VALUE obj, VALUE arg)
+{
+    if (!rb_respond_to(arg, id_cmp)) {
+	rb_notimplement();
+    }
+    return Qnil;
+}
+
 
 /***********************************************************************
@@ -2518,4 +2528,5 @@ Init_Object(void)
     rb_define_method(rb_mKernel, "=~", rb_obj_match, 1);
     rb_define_method(rb_mKernel, "!~", rb_obj_not_match, 1);
+    rb_define_method(rb_mKernel, "<=>", rb_obj_cmp, 1);
     rb_define_method(rb_mKernel, "eql?", rb_obj_equal, 1);
     rb_define_method(rb_mKernel, "hash", rb_obj_hash, 0);
@@ -2659,4 +2670,5 @@ Init_Object(void)
     id_inspect = rb_intern("inspect");
     id_init_copy = rb_intern("initialize_copy");
+    id_cmp = rb_intern("<=>");
 
     for (i=0; conv_method_names[i].method; i++) {


-- 
Nobu Nakada