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From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.unix.wizards
Subject: Re: Do start conditions work in lex?
Message-ID: <8706@mimsy.UUCP>
Date: Wed, 23-Sep-87 00:54:32 EDT
Article-I.D.: mimsy.8706
Posted: Wed Sep 23 00:54:32 1987
Date-Received: Sat, 26-Sep-87 00:48:03 EDT
References: <6@radix> <1516@epimass.EPI.COM>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 26
Keywords: lex, bug

>In article <6@radix> jimv@radix.UUCP (Jim Valerio) writes:
>>... it looks like lex is not doing the right thing with start conditions.

In article <1516@epimass.EPI.COM> jbuck@epimass.EPI.COM (Joe Buck) writes:
>Your problem is that a pattern without a start condition matches
>regardless of start condition.  So with the following lex code:

>>	0 		{ printf("0\n"); BEGIN Z; }
>>	1		{ printf("shouldn't get here!\n"); }
>>	<Z>1		{ printf("1\n"); }

>... Solution: reverse the order, to
>	0 		{ printf("0\n"); BEGIN Z; }
>	<Z>1		{ printf("1\n"); }
>	1		{ printf("shouldn't get here!\n"); }

Or use

	<INITIAL>1	{ printf("shouldn't get here!\n"); }
	<Z>1		{ printf("1\n"); }

Lex begins in state INITIAL; if there are no `%state's or BEGIN
directives, it stays that way forever.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris