# From beebe@math.utah.edu  Thu Aug  2 15:35:07 2001

# Received: from mail.actcom.co.il [192.114.47.13]

# 	by localhost with POP3 (fetchmail-5.7.4)

# 	for arnold@localhost (single-drop); Thu, 02 Aug 2001 15:35:07 +0300 (IDT)

# Received: by actcom.co.il (mbox arobbins)

#  (with Cubic Circle's cucipop (v1.31 1998/05/13) Thu Aug  2 16:02:36 2001)

# X-From_: beebe@sunshine.math.utah.edu Thu Aug  2 15:41:13 2001

# Received: from lmail.actcom.co.il by actcom.co.il  with ESMTP

# 	(8.9.1a/actcom-0.2) id PAA01349 for <arobbins@actcom.co.il>;

# 	Thu, 2 Aug 2001 15:41:06 +0300 (EET DST)  

# 	(rfc931-sender: mail.actcom.co.il [192.114.47.13])

# Received: from billohost.com (www.billohost.com [209.196.35.10])

# 	by lmail.actcom.co.il (8.11.2/8.11.2) with ESMTP id f72Cf3I21032

# 	for <arobbins@actcom.co.il>; Thu, 2 Aug 2001 15:41:05 +0300

# Received: from fencepost.gnu.org (we-refuse-to-spy-on-our-users@fencepost.gnu.org [199.232.76.164])

# 	by billohost.com (8.9.3/8.9.3) with ESMTP id IAA28585

# 	for <arnold@skeeve.com>; Thu, 2 Aug 2001 08:34:38 -0400

# Received: from sunshine.math.utah.edu ([128.110.198.2])

# 	by fencepost.gnu.org with esmtp (Exim 3.22 #1 (Debian))

# 	id 15SHjG-00036x-00

# 	for <arnold@gnu.org>; Thu, 02 Aug 2001 08:37:30 -0400

# Received: from suncore.math.utah.edu (IDENT:GsUbUdUYCtFLRE4HvnnvhN4JsjooYcfR@suncore0.math.utah.edu [128.110.198.5])

# 	by sunshine.math.utah.edu (8.9.3/8.9.3) with ESMTP id GAA00190;

# 	Thu, 2 Aug 2001 06:37:04 -0600 (MDT)

# Received: (from beebe@localhost)

# 	by suncore.math.utah.edu (8.9.3/8.9.3) id GAA20469;

# 	Thu, 2 Aug 2001 06:37:03 -0600 (MDT)

# Date: Thu, 2 Aug 2001 06:37:03 -0600 (MDT)

# From: "Nelson H. F. Beebe" <beebe@math.utah.edu>

# To: arnold@gnu.org

# Cc: beebe@math.utah.edu

# X-US-Mail: "Center for Scientific Computing, Department of Mathematics, 322

#         INSCC, University of Utah, 155 S 1400 E RM 233, Salt Lake City, UT

#         84112-0090, USA"

# X-Telephone: +1 801 581 5254

# X-FAX: +1 801 585 1640, +1 801 581 4148

# X-URL: http://www.math.utah.edu/~beebe

# Subject: awk implementations: a bug, or new dark corner?

# Message-ID: <CMM.0.92.0.996755823.beebe@suncore.math.utah.edu>

# Status: RO

# 

# Consider the following program:

# 

# % cat bug.awk

BEGIN {

    split("00/00/00",mdy,"/")

    if ((mdy[1] == 0) && (mdy[2] == 0) && (mdy[3] == 0))

    {

        print "OK: zero strings compare equal to number zero"

        exit(0)

    }

    else

    {

        print "ERROR: zero strings compare unequal to number zero"

        exit(1)

    }

}

# 

# Here are the awk implementation versions (on Sun Solaris 2.7):

# 

# 	% awk -V

# 	awk version 19990416

# 

# 	% mawk -W version

# 	mawk 1.3.3 Nov 1996, Copyright (C) Michael D. Brennan

# 

# 	% nawk -V

# 	awk version 20001115

# 

# 	% gawk --version

# 	GNU Awk 3.1.10

# 	...

# 

# Here's what they say about the test program:

# 

# 	foreach f (awk mawk nawk gawk gawk-*)

# 		echo ======== $f

# 		$f -f ~/bug.awk

# 	end

# 

# 	======== awk

# 	OK: zero strings compare equal to number zero

# 	======== mawk

# 	OK: zero strings compare equal to number zero

# 	======== nawk

# 	OK: zero strings compare equal to number zero

# 	======== gawk

# 	ERROR: zero strings compare unequal to number zero

# 	======== gawk-3.0.0

# 	OK: zero strings compare equal to number zero

# 	======== gawk-3.0.1

# 	OK: zero strings compare equal to number zero

# 	======== gawk-3.0.3

# 	OK: zero strings compare equal to number zero

# 	======== gawk-3.0.4

# 	OK: zero strings compare equal to number zero

# 	======== gawk-3.0.5

# 	OK: zero strings compare equal to number zero

# 	======== gawk-3.0.6

# 	OK: zero strings compare equal to number zero

# 	======== gawk-3.0.60

# 	OK: zero strings compare equal to number zero

# 	======== gawk-3.0.90

# 	ERROR: zero strings compare unequal to number zero

# 	======== gawk-3.0.91

# 	ERROR: zero strings compare unequal to number zero

# 	======== gawk-3.0.92

# 	ERROR: zero strings compare unequal to number zero

# 	======== gawk-3.0.93

# 	ERROR: zero strings compare unequal to number zero

# 	======== gawk-3.0.94

# 	ERROR: zero strings compare unequal to number zero

# 	======== gawk-3.0.95

# 	ERROR: zero strings compare unequal to number zero

# 	======== gawk-3.0.96

# 	ERROR: zero strings compare unequal to number zero

# 	======== gawk-3.0.97

# 	ERROR: zero strings compare unequal to number zero

# 	======== gawk-3.1.0

# 	ERROR: zero strings compare unequal to number zero

# 	======== gawk-3.1.10

# 	ERROR: zero strings compare unequal to number zero

# 

# Identical results were obtained on Apple Rhapsody, Apple Darwin,

# Compaq/DEC Alpha OSF/1, Intel x86 GNU/Linux, SGI IRIX 6.5, DEC Alpha

# GNU/Linux, and Sun SPARC GNU/Linux, so it definitely is not a C

# compiler problem.

# 

# However, the gray awk book, p. 44, says:

# 

# 	In a comparison expression like:

# 		x == y

# 	if both operands have a numeric type, the comparison is numeric;

# 	otherwise, any numeric operand is converted to a string and the

# 	comparison is made on the string values.

# 

# and the new green gawk book, p. 95, says:

# 

# 	When comparing operands of mixed types, numeric operands are

# 	converted to strings using the value of `CONVFMT'

# 

# This suggests that the OK response in bug.awk is wrong, and the ERROR

# response is correct.  Only recent gawk releases do the right thing,

# and it is awk, mawk, and nawk that have a bug.

# 

# If I change the test program from "00/00/00" to "0/0/0", all versions

# tested produce the OK response.

# 

# Comments?

# 

# After reading the two book excerpts, I changed my code to read

# 

#     if (((0 + mdy[1]) == 0) && ((0 + mdy[2]) == 0) && ((0 + mdy[3]) == 0))

# 

# and output from all implementations now agrees.

# 

# -------------------------------------------------------------------------------

# - Nelson H. F. Beebe                    Tel: +1 801 581 5254                  -

# - Center for Scientific Computing       FAX: +1 801 585 1640, +1 801 581 4148 -

# - University of Utah                    Internet e-mail: beebe@math.utah.edu  -

# - Department of Mathematics, 322 INSCC      beebe@acm.org  beebe@computer.org -

# - 155 S 1400 E RM 233                       beebe@ieee.org                    -

# - Salt Lake City, UT 84112-0090, USA    URL: http://www.math.utah.edu/~beebe  -

# -------------------------------------------------------------------------------

#