fact: Definition doubleI_def A B (T: fterm2) f := [/\ surjection f, source f = A \times B & forall p, inc p (A\times B) -> Vf f p = T p (restriction1 f (doubleI_E (P p) (Q p)))].
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)