proposition: Lemma cancel_precomposition (C : precategory_data) (a b c: C) (f f' : b --> c) (g : a --> b) : f = f' -> g · f = g · f'.
proof: Proof. apply maponpaths. Defined.
imports: UniMath.Foundations.Propositions UniMath.Foundations.Sets UniMath.MoreFoundations.PartA UniMath.MoreFoundations.Notations