%{
  (* Exprpar.grm: parser specification for the simple expression language *)

  open Absyn;
%}

%token <int> INT
%token <string> VAR
%token PLUS MINUS TIMES EQ
%token END IN LET
%token LPAR RPAR
%token EOF

%left MINUS PLUS        /* middle precedence  */
%left TIMES             /* highest precedence */

%start Main
%type <Absyn.expr> Main Expr

%%

Main:
    Expr EOF                            { $1 }
;

Expr:
    VAR                                 { Var $1  }
  | INT                                 { Int $1 }
  | MINUS Expr                          { Mminus $2 }
  | LPAR Expr RPAR                      { $2 }
  | LET VAR EQ Expr IN Expr END         { Let($2, $4, $6) }
  | Expr TIMES Expr                     { Times($1, $3) }  
  | Expr PLUS  Expr                     { Plus($1, $3) }  
  | Expr MINUS Expr                     { Minus($1, $3) } 
;