include "ground/notation/relations/doteq_4.ma".
include "ground/lib/relations.ma".
-(* EXTENSIONAL EQUIVALENCE **************************************************)
+(* EXTENSIONAL EQUIVALENCE FOR FUNCTIONS ************************************)
definition exteq (A,B:Type[0]): relation (A → B) ≝
λf1,f2. ∀a. f1 a = f2 a.
lemma exteq_canc_dx (A) (B): right_cancellable … (exteq A B).
/2 width=1 by exteq_repl/ qed-.
-(* Constructions with function composition **********************************)
+(* Constructions with compose ***********************************************)
lemma compose_repl_fwd_dx (A) (B) (C) (g) (f1) (f2):
f1 ≐{A,B} f2 → g ∘ f1 ≐{A,C} g ∘ f2.