Date:	Tue, 8 Jun 1999 19:25:20 -0400
Message-Id:	<199906082325.TAA25150@envy.delorie.com>
From:	DJ Delorie <dj AT delorie DOT com>
To:	djgpp AT delorie DOT com
In-reply-to:	<375DB01B.839CC62A@hotmail.com> (message from Denis Lamarche on
	Tue, 08 Jun 1999 21:11:49 GMT)
Subject:	Re: Bison Vs. Flex?
References:	<375DB01B DOT 839CC62A AT hotmail DOT com>
Reply-To:	djgpp AT delorie DOT com
X-Mailing-List:	djgpp AT delorie DOT com
X-Unsubscribes-To:	listserv AT delorie DOT com

> What is the difference between Bison And Flex?

A flex-built parser is a lexical analyzer.  Basically, it reads a text
file and converts it to "tokens" or words.  It sends those tokens to
the bison-built parser, which recognizes the syntax of those tokens
and takes actions based on them.

For example, a flex-built parser would see "if (x) exit" and convert
it into the following token stream:

	T_IF
	'('
	T_IDENTIFIER (name="x")
	')'
	T_IDENTIFIER (name="exit")

The bison-generated portion, for example, would match it against a
pattern like this (real parsers can be *very* complicated):

statements : IF '(' expression ')' statement { foo($3, $5); }
           | WHILE '(' expression ')' statement { bar($3, $5); }
           | statement
           ;

- Raw text -