fact: Definition continuous2d_at {U V W : TopologicalSpace} (f : U → V → W) (x : U) (y : V) := is_lim (λ z : U × V, f (pr1 z) (pr2 z)) (FilterDirprod (locally x) (locally y)) (f x y).
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.Topology.Filters UniMath.Algebra.Groups UniMath.Algebra.DivisionRig UniMath.Algebra.ConstructiveStructures