From 3acdde20a93874cd6395e2537b5f2cb36df8b022 Mon Sep 17 00:00:00 2001
From: Jeremy Yallop <yallop@gmail.com>
Date: Mon, 28 Sep 2015 16:58:09 +0100
Subject: [PATCH] Add CArray.fold_right

---
 src/ctypes/ctypes.mli           |  5 +++++
 src/ctypes/ctypes_memory.ml     |  7 +++++++
 tests/test-arrays/test_array.ml | 16 ++++++++++++++++
 3 files changed, 28 insertions(+)

diff --git a/src/ctypes/ctypes.mli b/src/ctypes/ctypes.mli
index b4e21ba7..c1c63f78 100644
--- a/src/ctypes/ctypes.mli
+++ b/src/ctypes/ctypes.mli
@@ -296,6 +296,11 @@ sig
          [(((x @ a.(0)) @ a.(1)) ...) @ a.(n-1)]
        where [n] is the length of the array [a]. *)
 
+  val fold_right : ('b -> 'a -> 'a) -> 'b t -> 'a -> 'a
+  (** [CArray.fold_right f a x] computes
+         [a.(0) @ (a.(1) @ ( ... (a.(n-1) @ x) ...))]
+       where [n] is the length of the array [a]. *)
+
   val length : 'a t -> int
   (** Return the number of elements of the given array. *)
 
diff --git a/src/ctypes/ctypes_memory.ml b/src/ctypes/ctypes_memory.ml
index d8adc90c..38a255c2 100644
--- a/src/ctypes/ctypes_memory.ml
+++ b/src/ctypes/ctypes_memory.ml
@@ -240,6 +240,13 @@ struct
       r := f !r (unsafe_get a i)
     done;
     !r
+
+  let fold_right f a x =
+    let r = ref x in
+    for i = length a - 1 downto 0 do
+      r := f (unsafe_get a i) !r
+    done;
+    !r
 end
 
 let make ?finalise s =
diff --git a/tests/test-arrays/test_array.ml b/tests/test-arrays/test_array.ml
index 0c81ae8a..f02c0067 100644
--- a/tests/test-arrays/test_array.ml
+++ b/tests/test-arrays/test_array.ml
@@ -147,6 +147,19 @@ let test_fold_left _ =
   assert_equal r []
 
 
+(*
+  Test the CArray.fold_right function
+ *)
+let test_fold_right _ =
+  let a = CArray.of_list int [1; 2; 3] in
+  let r = CArray.fold_right (Printf.sprintf "%d%s") a "." in
+  assert_equal "123." r;
+    
+  let a = CArray.of_list int [] in
+  let r = CArray.fold_right (fun _ -> assert false) a [] in
+  assert_equal r []
+
+
 (*
   Test that creating an array initializes all elements appropriately.
 *)
@@ -270,6 +283,9 @@ let suite = "Array tests" >:::
    "CArray.fold_left"
     >:: test_fold_left;
 
+   "CArray.fold_right"
+    >:: test_fold_right;
+
    "array initialization"
     >:: test_array_initialiation;