proposition: Lemma eq_constt pi1 pi2 x : pi1 =i pi2 -> x.`_pi1 = x.`_pi2.
proof: Proof. move=> pi12; congr (x ^+ (chinese _ _ 1 0)); apply: eq_partn => // a. by congr (~~ _); apply: pi12. Qed.
imports: mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq div) mathcomp(fintype bigop finset prime fingroup morphism) mathcomp(gfunctor automorphism quotient action gproduct) mathcomp(cyclic)