proposition: Lemma restrC A (d d': A -> Prop) r : restr_rel d (restr_rel d' r) ≡ restr_rel d' (restr_rel d r).
proof: Proof. u. Qed.
imports: Program.Basics Arith micromega.Lia Permutation List Setoid HahnBase HahnList HahnRelationsBasic HahnSets