proposition: Lemma cfSdprod_iso K H G (defG : K ><| H = G) : isometry (cfSdprod defG).
proof: Proof. move=> phi psi; have [/andP[_ nKG] _ _ _ _] := sdprod_context defG. by rewrite [cfSdprod _]locked_withE cfMorph_iso ?cfIsom_iso. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(div choice fintype tuple finfun bigop prime order) mathcomp(ssralg poly finset fingroup morphism perm) mathcomp(automorphism quotient finalg action gproduct) mathcomp(zmodp commutator cyclic center pgroup sylow) mathcomp(matrix vector falgebra ssrnum algC algnum) mathcomp(archimedean)