From: Martijn Dekker <martijn@inlv.org>
To: Zsh hackers list <zsh-workers@zsh.org>
Subject: [BUG] POSIX arith: inf, nan should be variables
Date: Mon, 15 Nov 2021 18:40:17 +0100 [thread overview]
Message-ID: <f45c480a-a7ac-54fc-4140-665ff98f9dc6@inlv.org> (raw)
$ zsh --emulate sh -c 'inf=1; nan=2; echo $((inf)) $((nan))'
Inf NaN
Expected: 1 2
This is a POSIX compliance issue that ksh93 also has (I've just fixed in
ksh 93u+m). I can see why this is needed for full floating point
arithmetic support, but in POSIX sh, all case variants of inf and nan
are perfectly legitimate variables that portable scripts should be able
to use, including in arithmetic evaluation. Their recognition should be
turned off for sh emulation, but not for ksh emulation as ksh93's native
mode also supports floating point arithmetic.
So, what shell option to tie that to? That's a bit difficult. It needs
to be an option that is on for sh, but off for ksh (or vice versa). A
comparison of 'set -o' output between sh and ksh modes shows that the
options are limited to the following:
bsdecho
ignorebraces
kshglob
kshoptionprint
localoptions
localtraps
octalzeroes
promptbang
sharehistory
singlelinezle
The only one of those that has anything to do with an arithmetic context
is octalzeroes, so that one may be the least bad one to choose. The
preliminary patch below does that.
Perhaps octalzeroes could be renamed to something like posixmath, so
that it becomes legitimate to attach this and any other POSIX arithmetic
quirks to this option without further crowding the shell option space.
Thoughts/opinions?
--- a/Src/math.c
+++ b/Src/math.c
@@ -863,7 +863,7 @@ zzlex(void)
p = ptr;
ptr = ie;
- if (ie - p == 3) {
+ if (ie - p == 3 && !isset(OCTALZEROES)) {
if ((p[0] == 'N' || p[0] == 'n') &&
(p[1] == 'A' || p[1] == 'a') &&
(p[2] == 'N' || p[2] == 'n')) {
--
|| modernish -- harness the shell
|| https://github.com/modernish/modernish
||
|| KornShell lives!
|| https://github.com/ksh93/ksh
next reply other threads:[~2021-11-15 17:40 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-15 17:40 Martijn Dekker [this message]
2021-11-16 9:06 ` Oliver Kiddle
2021-11-16 12:55 ` Vincent Lefevre
2021-11-28 20:34 ` Oliver Kiddle
2021-12-01 3:31 ` Daniel Shahaf
2021-12-01 3:37 ` Bart Schaefer
2021-12-01 4:27 ` Writing XFail tests (was: Re: [BUG] POSIX arith: inf, nan should be variables) Daniel Shahaf
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