fact: Definition split {x y z w : C} (f : x ~> y) (g : z ~> w) : x ⨂ z ~> y ⨂ w := fork (f ∘ proj_left) (g ∘ proj_right).
imports: Category.Lib Category.Theory.Category Category.Theory.Isomorphism Category.Theory.Functor Category.Structure.Monoidal.Relevance Category.Structure.Monoidal.Semicartesian