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From: erikb@botter.UUCP
Newsgroups: comp.os.minix
Subject: Re: expr(1) source - bug fix
Message-ID: <1139@botter.cs.vu.nl>
Date: Mon, 13-Apr-87 02:59:08 EST
Article-I.D.: botter.1139
Posted: Mon Apr 13 02:59:08 1987
Date-Received: Wed, 15-Apr-87 00:40:46 EST
Sender: remote@cs.vu.nl
Reply-To: erikb@cs.vu.nl (Erik Baalbergen)
Distribution: world
Organization: V.U. Informatica, Amsterdam
Lines: 44
Keywords: expr bugs

The following is a fix in reply to the bug (expr '(' 1 ')' + 1) as reported
by Barry Brachman. The '<' lines refer to the bug version, the '>' to the
fixed version.

Erik Baalbergen
-- cut here --
4c4,5
< 	expr ::= expr operator expr | "(" expr ")" ;
---
> 	expr ::= primary | primary operator expr ;
> 	primary ::= '(' expr ')' | signed-integer ;
49,50c50,51
< 	{"(",	LPAREN,	0},
< 	{")",	RPAREN,	0},
---
> 	{"(",	LPAREN,	-1},
> 	{")",	RPAREN,	-1},
128,131c129,135
< 		res = expr(lex(*++ip), MAXPRIO);
< 		if (lex(*++ip) != RPAREN)
< 			syntax();
< 		return res;
---
> 		if (prio == 0) {
> 			res = expr(lex(*++ip), MAXPRIO);
> 			if (lex(*++ip) != RPAREN)
> 				syntax();
> 		}
> 		else
> 			res = expr(n, prio - 1);
133c137,143
< 	if (n != OPERAND)
---
> 	else
> 	if (n == OPERAND) {
> 		if (prio == 0)
> 			return num(*ip);
> 		res = expr(n, prio - 1);
> 	}
> 	else
135,137d144
< 	if (prio == 0)
< 		return num(*ip);
< 	res = expr(n, prio - 1);