Section is_KHInt.
Context {V : NormedModule R_AbsRing}.
Definition is_KHInt (f : R -> V) (a b : R) (If : V) :=
filterlim (fun ptd => scal (sign (b-a)) (Riemann_sum f ptd)) (KH_fine a b) (locally If).
Definition ex_KHInt f a b :=
exists If : V, is_KHInt f a b If.

Lemma ex_KHInt_const :
forall (a b : R) (c : V),
ex_KHInt (fun x : R => c) a b.