Section FsetBigOps.
Variables (R : Type) (idx : R) (op : Monoid.com_law idx).
Let rhs_cond P K E :=
(\big[op/idx]_(A <- P) \big[op/idx]_(x <- A | K x) E x)%fset.
Let rhs P E := (\big[op/idx]_(A <- P) \big[op/idx]_(x <- A) E x)%fset.
End FsetBigOps.
End FsetPartitions.

Lemma iter_fix T n f (x : T) : f x = x -> iter n f x = x.