(* CMCS-312, 2006 Sample Parser  *)

open Ast

%%
%name Calc

%term 
  VAR of string
| NUM of int 
| REPEAT
| LPAREN
| RPAREN
| LAMBDA
| PLUS
| DOT
| STOP
| EOF

%nonterm 
  start of term option
| term of term
| app of term
| abs of term
| plus of term
| repeat of term
| atom of term

%pos int

%nodefault
%verbose

%start start
%eop STOP

%%

start:
  abs (SOME abs)
| (NONE)

abs:
  LAMBDA VAR DOT abs (Term_abs(VAR,abs))
| repeat (repeat)

repeat:
  REPEAT atom atom atom (Term_repeat(atom1,atom2,atom3))
| term (term)

term:
  term PLUS app (Term_plus(term,app))
| app (app)
 
app:
  app atom (Term_app (app, atom))
| atom (atom)

atom:
  VAR (Term_var VAR)
| NUM (Term_num NUM)
| LPAREN abs RPAREN (Term_paren abs)