module type synt =
sig
    type ide = Id of string 
    type exp = 
    	Eint of int 
      | Ebool of bool 
      | Var of ide
      | Pair of exp * exp
      | First of exp
      | Snd of exp
      | Prod of exp * exp
      | Sum of exp * exp
      | Diff of exp * exp
      | Eq of exp * exp
      | Minus of exp
      | Iszero of exp
      | Or of exp * exp
      | And of exp * exp
      | Not of exp
      | Ifthenelse of exp * exp * exp
      | Fun of ide * exp
      | Appl of exp * exp 
      | Letrec of ide * exp  * exp
      | Let of ide * exp * exp

end


module Expr : synt =
struct
    type ide = Id of string 
    type exp = 
    	Eint of int 
      | Ebool of bool 
      | Var of ide
      | Pair of exp * exp
      | First of exp
      | Snd of exp
      | Prod of exp * exp
      | Sum of exp * exp
      | Diff of exp * exp
      | Eq of exp * exp
      | Minus of exp
      | Iszero of exp
      | Or of exp * exp
      | And of exp * exp
      | Not of exp
      | Ifthenelse of exp * exp * exp
      | Fun of ide * exp
      | Appl of exp * exp 
      | Letrec of ide * exp  * exp
      | Let of ide * exp * exp

end