From: Elias Athanasopoulos <elathan@...>
Date: 2004-04-16T02:50:06+09:00
Subject: Re: Hash, ==,  key-value comparison

On Fri, Apr 16, 2004 at 02:30:02AM +0900, walter@mwsewall.com wrote:
> 
> > On Fri, Apr 16, 2004 at 02:04:10AM +0900, walter@mwsewall.com wrote: >
> > Ok, > > ALthough the docs don't mention it, Hash comparison using ==
> > checks > not only the key value pairs, but also the default value /
> > default > procs. > > So how does one compare 2 hashes key-value pairs.
> >  I can see that it 
> > 
> > I can contribute a patch to:
> > 
> > * Change '==' method to compare only key-value pairs.
> > * Add Hash#=== method to act like current Hash#==
> > 
> > Comments?
> >
> 
> Personally, I like the idea.  You get my vote!

I will add a ChangeLog entry if it is accepted.

elathan@velka:~/hacking/ruby> cat ../test.rb
h1 = { "a" => 1, "b" => 2}

h2 = Hash.new(2)
h2["a"] = 1
h2["b"] = 2

puts h1 == h2
puts h1 === h2
elathan@velka:~/hacking/ruby> ./ruby ../test.rb
true
false

Enjoy,
-- 
University of Athens			I bet the human brain 
Physics Department				is a kludge --Marvin Minsky 


--- /home/elathan/hacking/ruby/hash.c.orig	2004-04-15 04:46:29.000000000 +0300
+++ /home/elathan/hacking/ruby/hash.c	2004-04-15 04:52:39.000000000 +0300
@@ -1425,6 +1425,48 @@
     }
     if (RHASH(hash1)->tbl->num_entries != RHASH(hash2)->tbl->num_entries)
 	return Qfalse;
+
+    data.tbl = RHASH(hash2)->tbl;
+    data.result = Qtrue;
+    st_foreach(RHASH(hash1)->tbl, equal_i, (st_data_t)&data);
+
+    return data.result;
+}
+
+/*
+ *  call-seq:
+ *     hsh === other_hash    => true or false
+ *  
+ *  Equality---Two hashes are strictly equal if they each contain the same number
+ *  of keys and if each key-value pair is equal to (according to
+ *  <code>Object#==</code>) the corresponding elements in the other
+ *  hash. Both hashes must have also equal default values/procs.
+ *     
+ *     h1 = { "a" => 1, "c" => 2 }
+ *     h2 = { 7 => 35, "c" => 2, "a" => 1 }
+ *     h3 = { "a" => 1, "c" => 2, 7 => 35 }
+ *     h4 = { "a" => 1, "d" => 2, "f" => 35 }
+ *     h1 === h2   #=> false
+ *     h2 === h3   #=> true
+ *     h3 === h4   #=> false
+ *     
+ */
+
+static VALUE
+rb_hash_strict_equal(hash1, hash2)
+    VALUE hash1, hash2;
+{
+    struct equal_data data;
+
+    if (hash1 == hash2) return Qtrue;
+    if (TYPE(hash2) != T_HASH) {
+	if (!rb_respond_to(hash2, rb_intern("to_hash"))) {
+	    return Qfalse;
+	}
+	return rb_equal(hash2, hash1);
+    }
+    if (RHASH(hash1)->tbl->num_entries != RHASH(hash2)->tbl->num_entries)
+	return Qfalse;
     if (!(rb_equal(RHASH(hash1)->ifnone, RHASH(hash2)->ifnone) &&
 	  FL_TEST(hash1, HASH_PROC_DEFAULT) == FL_TEST(hash2, HASH_PROC_DEFAULT)))
 	return Qfalse;
@@ -1435,7 +1477,6 @@
 
     return data.result;
 }
-
 static int
 rb_hash_invert_i(key, value, hash)
     VALUE key, value;
@@ -2365,6 +2406,7 @@
     rb_define_method(rb_cHash,"inspect", rb_hash_inspect, 0);
 
     rb_define_method(rb_cHash,"==", rb_hash_equal, 1);
+    rb_define_method(rb_cHash,"===", rb_hash_strict_equal, 1);
     rb_define_method(rb_cHash,"[]", rb_hash_aref, 1);
     rb_define_method(rb_cHash,"fetch", rb_hash_fetch, -1);
     rb_define_method(rb_cHash,"[]=", rb_hash_aset, 2);