Hi,
I'm trying to parse an expression made up of various symbols and the
\frac{}{} operator from LaTeX, but my grammar fails miserably since
I'm new with bison.
Flex
------
"\\"[Ff]rac { return FUNC; }
"^" { return POW; }
"{" { return OP; }
"}" { return CP; }
[0-9]+ { yylval.ival = atoi(yytext); return NUMBER; }
m|ml|mp|dsa { yylval.strval = strdup(yytext); return ISU; }
\n { return EOL; }
[ \t] { }
. { }
bison
--------
%union {
struct ast *a;
char *strval;
int ival;
}
%debug
%type <a> exp fact
%token <strval> ISU
%token <ival> NUMBER
%token FUNC POW
%token EOL OP CP
%nonassoc POW
%%
calclist:
| calclist factor EOL {
printf("result >",eval($2));
}
;
exp: fact
| exp fact {$$ = newast('*',$1,$2)};
fact: ISU {$$ = newnum($1,1);}
| ISU POW NUMBER {$$ = newnum($1,$3);}
| FUNC OP factor CP OP factor CP { $$ = newast('/',$3,$6);};
The idea is that I evaluate such expressions symbolically. There's no
problem with the AST implementation, only the grammar remains an
issue. It fails even for simple cases
\frac{m}{mp}
nodetype /
nodetype K
mp^1
nodetype K
mp^1
I should pe able to manipulate product of fractions such as
\frac{m]{mp}\frac{mp}{m}
Or even \frac{\frac{m}{mp}}{m}. I tried various grammars but I really
can't get my head arround it. Any pointers ? What am I missing?
Thank you
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