let module Subst = FoSubst in
(*let compose subst1 subst2 =
let s1 = List.map (fun (x,t) -> (x, Subst.apply_subst subst2 t)) subst1 in
let module Subst = FoSubst in
(*let compose subst1 subst2 =
let s1 = List.map (fun (x,t) -> (x, Subst.apply_subst subst2 t)) subst1 in