fact: Hypothesis (preorder_r: preorder r) (substrate_r: substrate r = I) (directed_r: right_directed_on r I) (fgraph_E: fgraph E) (domain_E: domain E = I) (fgraph_f: fgraph f) (domain_f: domain f = r) (function_f: forall p, inc p r -> function_prop (Vg f p) (Vg E (P p)) (Vg E (Q p))) (compose_f: forall i j k, gle r i j -> gle r j k -> Vg f (J j k) \co Vg f (J i j) = Vg f (J i k)).
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)