Section is_RInt.
(** * Definition of Riemann integral *)
Context {V : NormedModule R_AbsRing}.
Definition is_RInt (f : R -> V) (a b : R) (If : V) :=
filterlim (fun ptd => scal (sign (b-a)) (Riemann_sum f ptd)) (Riemann_fine a b) (locally If).
Definition ex_RInt (f : R -> V) (a b : R) :=
exists If : V, is_RInt f a b If.
(** ** Usual properties *)
(** The integral between a and a is null *)
(** Swapping bounds *)
(** Integrable implies bounded *)
(** Extensionality *)
(** ** Constant functions *)
(** ** Composition *)
(** ** Chasles *)

Lemma is_RInt_Chasles_2 (f : R -> V) (a b c : R) l1 l2 :
a < b < c -> is_RInt f a c l1 -> is_RInt f a b l2 -> is_RInt f b c (minus l1 l2).