From 4962e042f3b2d7c5b089cec2dfe4e07a46bd2231 Mon Sep 17 00:00:00 2001
From: Cyprien Mangin
Date: Wed, 24 Jun 2015 13:48:08 +0200
Subject: Add a [CList.partitioni] function.

---
 lib/cList.ml  | 11 +++++++++++
 lib/cList.mli |  1 +
 2 files changed, 12 insertions(+)

(limited to 'lib')

diff --git a/lib/cList.ml b/lib/cList.ml
index ba592d13f3..3a792d4168 100644
--- a/lib/cList.ml
+++ b/lib/cList.ml
@@ -47,6 +47,8 @@ sig
     ('a -> 'b -> 'c -> 'd -> 'e) -> 'a list -> 'b list -> 'c list -> 'd list -> 'e list
   val filteri :
     (int -> 'a -> bool) -> 'a list -> 'a list
+  val partitioni :
+    (int -> 'a -> bool) -> 'a list -> 'a list * 'a list
   val smartfilter : ('a -> bool) -> 'a list -> 'a list
   val extend : bool list -> 'a -> 'a list -> 'a list
   val count : ('a -> bool) -> 'a list -> int
@@ -486,6 +488,15 @@ let filteri p =
   in
   filter_i_rec 0
 
+let partitioni p =
+  let rec aux i = function
+    | [] -> [], []
+    | x :: l ->
+        let (l1, l2) = aux (succ i) l in
+        if p i x then (x :: l1, l2)
+        else (l1, x :: l2)
+  in aux 0
+
 let rec sep_last = function
   | [] -> failwith "sep_last"
   | hd::[] -> (hd,[])
diff --git a/lib/cList.mli b/lib/cList.mli
index 9c7b815c15..b19d1a80fc 100644
--- a/lib/cList.mli
+++ b/lib/cList.mli
@@ -89,6 +89,7 @@ sig
   val map4 : ('a -> 'b -> 'c -> 'd -> 'e) -> 'a list -> 'b list -> 'c list ->
     'd list -> 'e list
   val filteri : (int -> 'a -> bool) -> 'a list -> 'a list
+  val partitioni : (int -> 'a -> bool) -> 'a list -> 'a list * 'a list
 
   val smartfilter : ('a -> bool) -> 'a list -> 'a list
   (** [smartfilter f [a1...an] = List.filter f [a1...an]] but if for all i
-- 
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