fact: Definition BQpair_aux C := [/\ fgraph C, domain C = Nat, forall n, natp n -> inc (Vg C n) (BQ \times BQ), forall n, natp n -> P (Vg C n) <q P (Vg C (csucc n))& forall n, natp n -> Q (Vg C (csucc n)) <q Q (Vg C n)].
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)