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From: hansen@pegasus.UUCP (Tony L. Hansen)
Newsgroups: net.bugs.usg,net.bugs.4bsd,net.bugs.v7,net.bugs.2bsd
Subject: Re: expr(1) fails on negative arguments (with fix)
Message-ID: <2795@pegasus.UUCP>
Date: Fri, 13-Jun-86 14:00:05 EDT
Article-I.D.: pegasus.2795
Posted: Fri Jun 13 14:00:05 1986
Date-Received: Tue, 17-Jun-86 19:04:45 EDT
References: <270@cirl.UUCP> <219@decvax.UUCP>
Reply-To: hansen@pegasus.UUCP (60545457-Tony L. Hansen;LZ 3B-315;6243)
Distribution: net
Organization: AT&T-IS Labs, Lincroft, NJ
Lines: 28
Keywords: expr, System V
Xref: watmath net.bugs.usg:503 net.bugs.4bsd:2164 net.bugs.v7:232 net.bugs.2bsd:370
Summary: System V fixed the problem

<	expr(1) fails to handle negative arguments correctly.
<	In particular, arithmetic operators will not accept
<	negative arguments.  Additionally,  comparison operators
<	use string comparison instead of arithmetic comparison
<	if the second argument is negative.

Like so many other things, this bug was fixed in System V. My UNIX System
Vr2 machine gives the following answers:

<		expr 0 + -1
<		non-numeric argument
	-1
<		expr -2 \> -1
<		1
	0

< Nice fix. Try "expr -5 * ---6". The problem cannot be correctly fixed w/out
< going all out and implementing UMINUS is the yacc grammar. Any takers?

<		expr -5 \* ---6
	expr: non-numeric argument
<		expr -5 \* -6
	30

Sorry, but I haven't looked at the expr code to see what the real fix was.

					Tony Hansen
					ihnp4!pegasus!hansen