proposition: Lemma big_condT (J : finType) (A : {pred J}) F : \big[op/idx]_(i in A | true) F i = \big[op/idx]_(i in A) F i.
proof: Proof. by apply: eq_bigl => i; exact: andbT. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq path) mathcomp(div fintype tuple finfun)