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/*
* expr.y : A simple yacc expression parser
* Based on the Bison manual example.
*/
%{
#include <stdio.h>
#include <math.h>
%}
%union {
float val;
}
%token NUMBER
%token PLUS MINUS MULT DIV EXPON
%token EOL
%token LB RB
%left MINUS PLUS
%left MULT DIV
%right EXPON
%type <val> exp NUMBER
%%
input :
| input line
;
line : EOL
| exp EOL { printf("%g\n",$1);}
exp : NUMBER { $$ = $1; }
| exp PLUS exp { $$ = $1 + $3; }
| exp MINUS exp { $$ = $1 - $3; }
| exp MULT exp { $$ = $1 * $3; }
| exp DIV exp { $$ = $1 / $3; }
| MINUS exp %prec MINUS { $$ = -$2; }
| exp EXPON exp { $$ = pow($1,$3);}
| LB exp RB { $$ = $2; }
;
%%
yyerror(char *message)
{
printf("%s\n",message);
}
int main(int argc, char *argv[])
{
yyparse();
return(0);
}
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