1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
|
# 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 -
# -------------------------------------------------------------------------------
#
|
