+type term = I | S | K | FA of (term * term)
+
+let skomega = FA (FA (FA (S,I), I), FA (FA (S,I), I))
+let test = FA (FA (K,I), skomega)
+
+let reduce_one_step (t:term):term = match t with
+ FA(I,a) -> a
+ | FA(FA(K,a),b) -> a
+ | FA(FA(FA(S,a),b),c) -> FA(FA(a,c),FA(b,c))
+ | _ -> t
+
+let is_redex (t:term):bool = not (t = reduce_one_step t)
+
+let rec reduce_eager (t:term):term = match t with
+ I -> I
+ | K -> K
+ | S -> S
+ | FA (a, b) ->
+ let t' = FA (reduce_eager a, reduce_eager b) in
+ if (is_redex t') then reduce_eager (reduce_one_step t')
+ else t'
+
+let rec reduce_lazy (t:term):term = match t with
+ I -> I
+ | K -> K
+ | S -> S
+ | FA (a, b) ->
+ let t' = FA (reduce_lazy a, b) in
+ if (is_redex t') then reduce_lazy (reduce_one_step t')
+ else t'