GNU bug report logs - #13345
24.2.91; Wrong assumption in a hash table example + fix

Previous Next

To add a comment to this bug, you must first unarchive it, by sending
a message to control AT debbugs.gnu.org, with unarchive 13345 in the body.
You can then email your comments to 13345 AT debbugs.gnu.org in the normal way.

Toggle the display of automated, internal messages from the tracker.

Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Ari Roponen <ari.roponen <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.2.91; Wrong assumption in a hash table example + fix
Date: Thu, 03 Jan 2013 14:01:17 +0200

In file doc/lispref/hash.texi, there is an example:

    @example
    (defun case-fold-string= (a b)
      (compare-strings a nil nil b nil nil t))
    (defun case-fold-string-hash (a)
      (sxhash (upcase a)))

    (define-hash-table-test 'case-fold
      'case-fold-string= 'case-fold-string-hash)

    (make-hash-table :test 'case-fold)
    @end example

The documentation of `define-hash-table-test' says:

    The function @var{test-fn} should accept two arguments, two keys, and
    return non-@code{nil} if they are considered ``the same''.

In the above example, the test function returns always non-nil, because
it assumes `compare-strings' returns nil for differing strings. The
patch below fixes this wrong assumption.


2013-01-03  Ari Roponen  <ari.roponen <at> gmail.com>  (tiny change)

	* hash.texi (Defining Hash): Fix example.


=== modified file 'doc/lispref/hash.texi'
--- doc/lispref/hash.texi	2013-01-01 09:11:05 +0000
+++ doc/lispref/hash.texi	2013-01-03 10:50:19 +0000
@@ -293,7 +293,7 @@
 
 @example
 (defun case-fold-string= (a b)
-  (compare-strings a nil nil b nil nil t))
+  (eq t (compare-strings a nil nil b nil nil t)))
 (defun case-fold-string-hash (a)
   (sxhash (upcase a)))
 


In GNU Emacs 24.2.91.9 (x86_64-unknown-linux-gnu, GTK+ Version 3.7.2)
 of 2013-01-03 on arirop
Bzr revision: 111125 rgm <at> gnu.org-20130103063325-sx99hs1usiuqlxvb
Windowing system distributor `Fedora Project', version 11.0.11300000
System Description:	Fedora release 18 (Spherical Cow)

-- 
Ari Roponen

Message #10 received at 13345-done <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: 13345-done <at> debbugs.gnu.org
Subject: Re: bug#13345: 24.2.91; Wrong assumption in a hash table example + fix
Date: Thu, 03 Jan 2013 13:41:30 -0500

Version: 24.2.92

Thanks, applied.
You have a few tiny changes now. Please consider completing a copyright
assignment if you expect to contribute more (forgive me if I already
mentioned this).

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.