Library Stdlib.Logic.RelationalChoice

This file axiomatizes the relational form of the axiom of choice

Axiom relational_choice :
  forall (A B : Type) (R : A ->B ->Prop),
   (forall x : A, exists y : B , R x y ) ->
     exists R' : A ->B ->Prop,
       subrelation R' R /\ forall x : A, exists ! y : B , R' x y.