/*
** Base calculator grammar — four arithmetic operations.
**
** Token codes are assigned sequentially starting from 1 in declaration order:
**   PLUS=1, MINUS=2, TIMES=3, DIVIDE=4, LPAREN=5, RPAREN=6, INTEGER=7
**
** The extended grammar (calc_power.lime) appends CARET=8.  When the
** tokenizer produces code 8 and this parser receives it, the syntax_error
** handler fires because CARET is not in this grammar's token table.
*/

%name Calc
%token_type {int}
%type expr {int}
%extra_argument {int *result}

%include {
#include <stdio.h>
#include <assert.h>
}

%syntax_error {
    (void)yymajor;
    (void)yyminor;
    fprintf(stderr, "syntax error\n");
    *result = 0;
}

/* Tokens — declaration order determines integer codes */
%token PLUS.
%token MINUS.
%token TIMES.
%token DIVIDE.
%token LPAREN.
%token RPAREN.
%token INTEGER.

/* Precedence (lowest to highest) */
%left PLUS MINUS.
%left TIMES DIVIDE.
%right UMINUS.

%start_symbol program

program ::= expr(A). { *result = A; }

expr(A) ::= expr(B) PLUS expr(C).     { A = B + C; }
expr(A) ::= expr(B) MINUS expr(C).    { A = B - C; }
expr(A) ::= expr(B) TIMES expr(C).    { A = B * C; }
expr(A) ::= expr(B) DIVIDE expr(C).   {
    if (C == 0) {
        fprintf(stderr, "division by zero\n");
        A = 0;
    } else {
        A = B / C;
    }
}
expr(A) ::= MINUS expr(B). [UMINUS]   { A = -B; }
expr(A) ::= LPAREN expr(B) RPAREN.    { A = B; }
expr(A) ::= INTEGER(B).               { A = B; }