Any YACC / BISON gurus out there?

[Nick Crossley]

In article <1341 at ssf> richard at ssf.uucp (Richard Thombs) writes:
>I need to be able to get YACC (or BISON if need be) to fail a parse when an
>action tells it to.

Some versions of yacc have a YYBACKUP macro in the parser skeleton.
This allows limited backup, possibly not as much as you want.  I have
found it most useful to reduce the number of 'reserved words' in a
grammar:

rule	:	identifier	{ YYBACKUP(special($1)); }
	|	token1		{ ... }
	|	token2		{ ... }
	...
	;

The lexer never returns 'token1', etc.  The function 'special'
examines the identifier and returns token1, etc., as appropriate.
So token1, etc., are only recognised as keywords in the correct context;
elsewhere, they are just identifiers.
-- 

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Nick Crossley, ICL NA, 9801 Muirlands, Irvine, CA 92718-2521, USA 714-458-7282
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