grammar question

saleem@synopsys.com (Saleem Haider)
14 Mar 1996 17:26:43 -0500

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From: saleem@synopsys.com (Saleem Haider)
Newsgroups: comp.compilers
Date: 14 Mar 1996 17:26:43 -0500
Organization: Synopsys, Inc.
Keywords: yacc, parse, question

I need some pointers on how to write the grammar for expressions
that allow implied products, e.g. "a + b c + d" is "a + b*c +d"
and "(a + b) !c" is "(a + b) * (!c)". The regular cases are
handled by


%left '+'
%left '*'
exp: '(' exp ')'
| exp '+' exp
| exp '*' exp
;


I'd like to be able to add a rule like "| exp exp %prec MUL"
but that doesn't work.


I'd appreciate any pointers. I can use either yacc or bison.


Saleem
[Try this:


%left '+'
%left '*'
%token TOKEN
%%
bigexp:
exp | bigexp exp ;


exp: '(' exp ')'
| exp '+' exp
| exp '*' exp
                | TOKEN
;


-John]


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