From 8c44f7c63ee0c57936759408943ff611d630dda3 Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Mon, 18 Feb 2013 17:04:24 +0100
Subject: [PATCH] added flatMap to the combinators

---
 sequence.ml  | 10 ++++++++--
 sequence.mli |  4 ++++
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/sequence.ml b/sequence.ml
index 632fab9..b1a562c 100644
--- a/sequence.ml
+++ b/sequence.ml
@@ -99,10 +99,16 @@ let append s1 s2 =
 
 (** Concatenate a sequence of sequences into one sequence *)
 let concat s =
-  fun k ->
+  from_iter (fun k ->
     (* function that is called on every sub-sequence *)
     let k_seq seq = iter k seq in
-    s k_seq
+    s k_seq)
+
+(** Monadic bind. It applies the function to every element of the
+    initial sequence, and calls [concat]. *)
+let flatMap f seq =
+  from_iter
+    (fun k -> seq (fun x -> (f x) k))
 
 exception ExitSequence
 
diff --git a/sequence.mli b/sequence.mli
index ed1a640..3c377d0 100644
--- a/sequence.mli
+++ b/sequence.mli
@@ -95,6 +95,10 @@ val append : 'a t -> 'a t -> 'a t
 val concat : 'a t t -> 'a t
   (** Concatenate a sequence of sequences into one sequence *)
 
+val flatMap : ('a -> 'b t) -> 'a t -> 'b t
+  (** Monadic bind. It applies the function to every element of the
+      initial sequence, and calls [concat]. *)
+
 val take : int -> 'a t -> 'a t
   (** Take at most [n] elements from the sequence *)