From 92205b6c36d55ba7f84471eddf7155b831614551 Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Thu, 14 Sep 2017 09:12:34 +0200
Subject: [PATCH] add `Sequence.pair_with_idx`

---
 src/Sequence.ml  | 4 ++++
 src/Sequence.mli | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/src/Sequence.ml b/src/Sequence.ml
index 5ecfd23..a9c0f96 100644
--- a/src/Sequence.ml
+++ b/src/Sequence.ml
@@ -971,6 +971,10 @@ let of_list l k = List.iter k l
 let on_list f l =
   to_list (f (of_list l))
 
+let pair_with_idx seq k =
+  let r = ref 0 in
+  seq (fun x -> let n = !r in incr r; k (n,x))
+
 let to_opt = head
 
 let of_opt o k = match o with
diff --git a/src/Sequence.mli b/src/Sequence.mli
index d3effc8..2d686da 100644
--- a/src/Sequence.mli
+++ b/src/Sequence.mli
@@ -495,6 +495,10 @@ val on_list : ('a t -> 'b t) -> 'a list -> 'b list
     @since 0.5.2
 *)
 
+val pair_with_idx : 'a t -> (int * 'a) t
+(** Similar to {!zip_i} but returns a normal sequence of tuples
+    @since NEXT_RELEASE *)
+
 val to_opt : 'a t -> 'a option
 (** Alias to {!head}
     @since 0.5.1 *)