open Format
open Syntax
open Support.Error
open Support.Pervasive

(* ------------------------   EVALUATION  ------------------------ *)

let rec isval ctx t = match t with
    TmAbs(_,_,_) -> true
  | _ -> false

exception NoRuleApplies

let rec eval ctx t = match t with
    _ when isval ctx t -> t
  | TmApp(fi,t1,t2) ->
      (match eval ctx t1 with
	 TmAbs(_,_,t12) ->
	   let v2 = eval ctx t2 in
	   eval ctx (termSubstTop v2 t12)
       | _ -> raise NoRuleApplies)
  | _ -> raise NoRuleApplies