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