proposition: Lemma big_ord_narrow_cond_leq : forall n1 n2 (P : pred 'I_(n2.+1)) F, forall le_n1_n2 : n1 <= n2, let w := @widen_ord n1.+1 n2.+1 le_n1_n2 in \big[op/idx]_(i < n2.+1 | P i && (i <= n1)) F i === \big[op/idx]_(i < n1.+1 | P (w i)) F (w i).
proof: Proof. move=> n1 n2; exact: big_ord_narrow_cond n1.+1 n2.+1. Qed.
imports: ssreflect ssrbool ssrfun eqtype ssrnat seq div choice fintype finfun paths Setoid Morphisms OperationClasses bigops