From: "Campbell, Rolf [SKY:1U32:EXCH]" <cp1v45 AT americasm01 DOT nt DOT com>
Newsgroups: comp.os.msdos.djgpp,comp.programming
Subject: Re: Bison and [f]lexical tie-ins
Date: Mon, 12 Jul 1999 10:40:24 -0400
Organization: Nortel Networks
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Martin Str|mberg wrote:

> Endlisnis (s257m AT unb DOT ca) wrote:
> :     That is sort-of what I've been doing, but to do the parsing correctly, I need to
> : know if "b" is a type-specifier or an ID.  And the reduce/reduce errors are in the
> No. At the parsing stage, it seems to me from your problem desciption,
> all you know is that "b" is an ID (which could be a type or a
> variable).

The code was (C++):

struct {int c,d;} b;
b={1,2};

Here, 'b' is a variable-name, and should be known as a variable-name in the parsing stage
immediately after the ";".  But, because of Bison's (or yacc's) look-ahead token, the 2nd
'b' has already been tokenized as an ID, which is not allowed as an rValue in an
expression, thus producing a parse error.

The real, IMPORTANT question (for a bison/yacc expert):
Is there any way to change the type associated with a token that already exists in the
Bison/yacc internal array of tokens.  If that is unclear, maybe this code fragment will
help. (this is incomplete and would not work without extensive modification)

#define ID 889
#define VAR 890

int yylex() {return ID;}

//Inside Bison/yacc code
decl:  ID ";" {_yacc_internal[value] = VAR;}

assignment:  VAR '=' ID

What I want is the "assignment" rule to be executed even though the "VAR" id never gets
returned (please ignore the fact that yylex will never return ";" or "=").  As I
understand, bison stores the return values from yylex in an array which gets shifted and
combined using all of the rules.  Is there any way that I can modify the contents of that
array.

--
     -Rolf Campbell (39)3-6318