End disc_mor_setoid.
Definition Comp_Discr_mor (a b c : U) (f : Discr_mor a b) :=
match f in (Discr_mor d d0) return (Discr_mor d0 c -> Discr_mor d c) with
| Build_Discr_mor x =>
fun g : Discr_mor x c =>
match g in (Discr_mor d d0) return (Discr_mor d d0) with
| Build_Discr_mor x => Build_Discr_mor x
end
end.

Lemma Idl_Discr : Idl_law Comp_Discr Id_Discr.