/*

 * 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);

}