From 43e150c212c311aa9dbf535faa756b34bf7f580a Mon Sep 17 00:00:00 2001
From: "Richard W.M. Jones" <rjones@redhat.com>
Date: Wed, 8 Oct 2014 14:59:52 +0100
Subject: [PATCH] mllib: Add 'combine3' function.

---
 mllib/common_utils.ml  | 6 ++++++
 mllib/common_utils.mli | 3 +++
 2 files changed, 9 insertions(+)

diff --git a/mllib/common_utils.ml b/mllib/common_utils.ml
index d3fec0671..ba39b7072 100644
--- a/mllib/common_utils.ml
+++ b/mllib/common_utils.ml
@@ -199,6 +199,12 @@ let rec mapi i f =
     r :: mapi (i + 1) f l
 let mapi f l = mapi 0 f l
 
+let rec combine3 xs ys zs =
+  match xs, ys, zs with
+  | [], [], [] -> []
+  | x::xs, y::ys, z::zs -> (x, y, z) :: combine3 xs ys zs
+  | _ -> invalid_arg "combine3"
+
 (* ANSI terminal colours. *)
 let ansi_green ?(chan = stdout) () =
   if TTY.isatty_stdout () then output_string chan "\x1b[0;32m"
diff --git a/mllib/common_utils.mli b/mllib/common_utils.mli
index 5bf4fbabf..71ccb4c3d 100644
--- a/mllib/common_utils.mli
+++ b/mllib/common_utils.mli
@@ -53,6 +53,9 @@ val iteri : (int -> 'a -> 'b) -> 'a list -> unit
 val mapi : (int -> 'a -> 'b) -> 'a list -> 'b list
 (** Various higher-order functions. *)
 
+val combine3 : 'a list -> 'b list -> 'c list -> ('a * 'b * 'c) list
+(** Like {!List.combine} but for triples.  All lists must be the same length. *)
+
 val make_message_function : quiet:bool -> ('a, unit, string, unit) format4 -> 'a
 (** Timestamped progress messages.  Used for ordinary messages when
     not [--quiet]. *)