/* calculator. */
%{

#include <stdio.h>
#include <stdlib.h>
#include "lexer.h"

void yyerror(const char *msg);

// Here is an example how to create custom data structure
typedef struct custom_data {
   char* name;
   int counter;
} custom_data;

%}

%union{
  double dval;
  int ival;
  struct custom_data* cval; // define the pointer type for custom data structure
}

%define parse.error verbose
%locations

%start input
%token MULT DIV PLUS MINUS EQUAL L_PAREN R_PAREN END
%token <dval> NUMBER
%type <dval> exp
%type <cval> input
%left PLUS MINUS
%left MULT DIV
%nonassoc UMINUS

%%

input: {
    $$ = malloc(sizeof(custom_data)); $$->name = "input"; $$->counter = 0;
}
| input line {
    $$ = $1; $1->counter++;
}
;

line: exp EQUAL END { printf("\t%f\n", $1); };

exp: NUMBER { $$ = $1; }
| exp PLUS exp { $$ = $1 + $3; }
| exp MINUS exp { $$ = $1 - $3; }
| exp MULT exp { $$ = $1 * $3; }
| exp DIV exp {
    if ($3==0) yyerror("divide by zero"); else $$ = $1 / $3;
}
| MINUS exp %prec UMINUS { $$ = -$2; }
| L_PAREN exp R_PAREN { $$ = $2; }
;
%%

int main(int argc, char **argv)
{
    if (argc > 1) {
        yyin = fopen(argv[1], "r");
        if (yyin == NULL){
            printf("syntax: %s filename\n", argv[0]);
        }
    }
    yyparse(); // Calls yylex() for tokens.
    return 0;
}

void yyerror(const char *msg)
{
    printf("** Line %d: %s\n", yylloc.first_line, msg);
}