Section BigConst.
Variables (R : Type) (idx : R) (op : R -> R -> R).

Lemma big_rmcond_in (I : eqType) (r : seq I) (P : pred I) F :
(forall i, i \in r -> ~~ P i -> F i = 1) ->
\big[*%M/1]_(i <- r | P i) F i = \big[*%M/1]_(i <- r) F i.