/*
 * Copyright (C) 2018 Nick Downing <nick@ndcode.org>
 * SPDX-License-Identifier: GPL-2.0-only
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; version 2.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51
 * Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
 */

%{
  import t_def
  import sys
%}

%locations

%token NUM

%left '+' '-'
%left '*' '/'
%right UMINUS

%%

S : S E '\n' {
    sys.stdout.write('Answer: {0:g}\nEnter an expression:\n'.format($2))
  }
  | S '\n'
  |
  | error '\n' {
  yyerror('Error, please try again:\n')
  yyerrok()
}
  ;
E : %space (?E{t_def.AST.Add}E '+' E) {
    $$ = $1 + $3
  }
  | %space (?E{t_def.AST.Sub}E '-' E) {
    $$ = $1 - $3
  }
  | %space (?E{t_def.AST.Mul}E '*' E) {
    $$ = $1 * $3
  }
  | %space (?E{t_def.AST.Div}E '/' E) {
    $$ = $1 / $3
  }
  | '(' E ')' {
    $$ = $2
  }
  | %space (?E{t_def.AST.Neg}'-' E) %prec UMINUS {
    $$ = -$2
  }
  | NUM
  ;
%%

def yyerror(s):
  sys.stdout.write('{0:s}\n'.format(s))
  sys.exit(1)