From f3cdb0943eea76d887367f7f7595f36507f7a373 Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Mon, 7 Jul 2014 13:41:15 +0200
Subject: [PATCH] monadic operator in CCList: map_m_par

---
 core/CCList.ml  | 9 +++++++++
 core/CCList.mli | 5 +++++
 2 files changed, 14 insertions(+)

diff --git a/core/CCList.ml b/core/CCList.ml
index 72d5ff87..2fca2327 100644
--- a/core/CCList.ml
+++ b/core/CCList.ml
@@ -526,6 +526,15 @@ module Traverse(M : MONAD) = struct
           aux f (x' :: acc) tail
     in aux f [] l
 
+  let rec map_m_par f l = match l with
+    | [] -> M.return []
+    | x::tl ->
+        let x' = f x in
+        let tl' = map_m_par f tl in
+        x' >>= fun x' ->
+        tl' >>= fun tl' ->
+        M.return (x'::tl')
+
   let sequence_m l = map_m (fun x->x) l
 
   let rec fold_m f acc l = match l with
diff --git a/core/CCList.mli b/core/CCList.mli
index 281a6616..6a72b547 100644
--- a/core/CCList.mli
+++ b/core/CCList.mli
@@ -236,6 +236,11 @@ module Traverse(M : MONAD) : sig
   val fold_m : ('b -> 'a -> 'b M.t) -> 'b -> 'a t -> 'b M.t
 
   val map_m : ('a -> 'b M.t) -> 'a t -> 'b t M.t
+
+  val map_m_par : ('a -> 'b M.t) -> 'a t -> 'b t M.t
+  (** Same as {!map_m} but [map_m_par f (x::l)] evaluates [f x] and
+      [f l] "in parallel" before combining their result (for instance
+      in Lwt). *)
 end
 
 (** {2 Conversions} *)