diff --git a/ChangeLog b/ChangeLog
index abb1df4707..c84f86365c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+Mon Sep 11 16:52:37 2006  Yukihiro Matsumoto  <matz@ruby-lang.org>
+
+	* hash.c (rb_hash_identical): a new method to make a hash to
+	  compare keys by their identity.
+
+	* hash.c (rb_hash_identical_p): new method to tell if a hash is
+	  identical or not.
+
+	* st.c (st_numcmp, st_numhash): export hash type functions.
+
 Mon Sep 11 11:42:21 2006  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* lib/rexml/source.rb (REXML::Source::encoding): should not
diff --git a/hash.c b/hash.c
index 10acf1487a..337007c39e 100644
--- a/hash.c
+++ b/hash.c
@@ -368,7 +368,7 @@ rb_hash_rehash(VALUE hash)
 	rb_raise(rb_eRuntimeError, "rehash during iteration");
     }
     rb_hash_modify(hash);
-    tbl = st_init_table_with_size(&objhash, RHASH(hash)->tbl->num_entries);
+    tbl = st_init_table_with_size(RHASH(hash)->tbl->type, RHASH(hash)->tbl->num_entries);
     rb_hash_foreach(hash, rb_hash_rehash_i, (st_data_t)tbl);
     st_free_table(RHASH(hash)->tbl);
     RHASH(hash)->tbl = tbl;
@@ -1475,6 +1475,54 @@ rb_hash_merge(VALUE hash1, VALUE hash2)
     return rb_hash_update(rb_obj_dup(hash1), hash2);
 }
 
+static struct st_hash_type identhash = {
+    st_numcmp,
+    st_numhash,
+};
+
+/*
+ *  call-seq:
+ *     hsh.identical => hsh
+ *  
+ *  Makes <i>hsh</i> to compare its keys by their identity, i.e. it
+ *  will consider exact same objects as same keys.
+ *     
+ *     h1 = { "a" => 100, "b" => 200, :c => "c" }
+ *     h1["a"]        #=> "a"
+ *     h1.identical
+ *     h1.identical?  #=> true
+ *     h1["a"]        #=> nil  # different objects.
+ *     h1[:c]         #=> "c"  # same symbols are all same.
+ *     
+ */
+
+static VALUE
+rb_hash_identical(VALUE hash)
+{
+    rb_hash_modify(hash);
+    RHASH(hash)->tbl->type = &identhash;
+    rb_hash_rehash(hash);
+    return hash;
+}
+
+/*
+ *  call-seq:
+ *     hsh.identical? => true or false
+ *  
+ *  Returns <code>true</code> if <i>hsh</i> will compare its keys by
+ *  their identity.  Also see <code>Hash#identical</code>.
+ *     
+ */
+
+static VALUE
+rb_hash_identical_p(VALUE hash)
+{
+    if (RHASH(hash)->tbl->type == &identhash) {
+	return Qtrue;
+    }
+    return Qfalse;
+}
+
 static int path_tainted = -1;
 
 static char **origenviron;
@@ -2324,6 +2372,9 @@ Init_Hash(void)
     rb_define_method(rb_cHash,"key?", rb_hash_has_key, 1);
     rb_define_method(rb_cHash,"value?", rb_hash_has_value, 1);
 
+    rb_define_method(rb_cHash,"identical", rb_hash_identical, 0);
+    rb_define_method(rb_cHash,"identical?", rb_hash_identical_p, 0);
+
 #ifndef __MACOS__ /* environment variables nothing on MacOS. */
     origenviron = environ;
     envtbl = rb_obj_alloc(rb_cObject);
diff --git a/st.c b/st.c
index 0ace74e235..88d79f8d70 100644
--- a/st.c
+++ b/st.c
@@ -38,11 +38,9 @@ struct st_table_entry {
      *
      */
 
-static int numcmp(long, long);
-static int numhash(long);
 static struct st_hash_type type_numhash = {
-    numcmp,
-    numhash,
+    st_numcmp,
+    st_numhash,
 };
 
 /* extern int strcmp(const char *, const char *); */
@@ -589,14 +587,14 @@ strhash(register const char *string)
     return hval;
 }
 
-static int
-numcmp(long x, long y)
+int
+st_numcmp(long x, long y)
 {
     return x != y;
 }
 
-static int
-numhash(long n)
+int
+st_numhash(long n)
 {
     return n;
 }
diff --git a/st.h b/st.h
index 4dad9c5f04..45609ddeb1 100644
--- a/st.h
+++ b/st.h
@@ -60,11 +60,7 @@ void st_add_direct(st_table *, st_data_t, st_data_t);
 void st_free_table(st_table *);
 void st_cleanup_safe(st_table *, st_data_t);
 st_table *st_copy(st_table *);
-
-#define ST_NUMCMP	((int (*)()) 0)
-#define ST_NUMHASH	((int (*)()) -2)
-
-#define st_numcmp	ST_NUMCMP
-#define st_numhash	ST_NUMHASH
+int st_numcmp(long, long);
+int st_numhash(long);
 
 #endif /* ST_INCLUDED */