/*
 * parser.mly
 * Parser for lambda
 * There should be 10 shift-reduce conflicts.
 */

%{
  (* This is where ocaml declarations go *)
  (* open Node *)
%}

%token <int> INT
%token <string> IDENT
%token LET IN EQUAL LAMBDA LPAREN RPAREN DOT EOF SEMI POUND

%start program /* the entry point */

%type <Lambda.exp list> program



%%

program:
    declaration SEMI program { $3 }
  | expression SEMI program { $1::$3 }
  | SEMI program { $2 }
  | EOF { [] };

declaration:
    LET IDENT EQUAL dexp
    {
      (*print_string "Parsed: ";
      Lambda.print $4;
      print_newline();*)
      Lambda.var_env := ($2,$4)::!Lambda.var_env
    };

dexp:
    LET IDENT EQUAL expression IN dexp
    {
      (*print_string "Parsed sub exp";
      print_newline();*)
      Lambda.Apply(Lambda.Lambda($2,$6),$4)
    }
  | expression { $1 }

expression:
    simpexp
    { $1 }
  | application
    { $1 };

simpexp:
    IDENT
    { Lambda.Var($1,0) }
  | POUND INT
    { Lambda.Var("",$2) }
  | INT
    { Lambda.Num($1) }
  /* | LPAREN expression RPAREN */
  | LPAREN dexp RPAREN
    { $2 }
  | abstraction
    { $1 }
    

abstraction:
    /* LAMBDA IDENT DOT expression */
    LAMBDA IDENT DOT dexp
    { Lambda.Lambda($2,$4) };
  /* | LAMBDA expression */
  | LAMBDA dexp
    { Lambda.Lambda("",$2) };

application:
    application simpexp
    { Lambda.Apply($1,$2) }
  | simpexp simpexp
    { Lambda.Apply($1,$2) }; 


%%

(* End of parser.mly *)