Stdlib: add List.map_last and List.iter_last

Author: vouillon

compiler/lib/generate.ml

@@ -61,15 +61,6 @@ let list_group f g l =
   | [] -> []
   | a :: r -> list_group_rec f g r (f a) [ g a ] []
 
-(* like [List.map] except that it calls the function with
-   an additional argument to indicate whether we're mapping
-   over the last element of the list *)
-let rec map_last f l =
-  match l with
-  | [] -> assert false
-  | [ x ] -> [ f true x ]
-  | x :: xs -> f false x :: map_last f xs
-
 (****)
 
 type application_description =
@@ -1816,7 +1807,7 @@ and compile_decision_tree st loop_stack backs frontier interm loc cx dtree =
         let l =
           List.flatten
             (List.map l ~f:(fun (ints, br) ->
-                 map_last (fun last i -> int i, if last then br else []) ints))
+                 List.map_last ~f:(fun last i -> int i, if last then br else []) ints))
         in
         !all_never, [ J.Switch_statement (cx, l, Some last, []), loc ]
   in

compiler/lib/stdlib.ml

@@ -271,6 +271,26 @@ module List = struct
       | x :: xs -> aux (x :: acc) xs
     in
     aux [] xs
+
+  (* like [List.map] except that it calls the function with
+     an additional argument to indicate whether we're mapping
+     over the last element of the list *)
+  let rec map_last ~f l =
+    match l with
+    | [] -> assert false
+    | [ x ] -> [ f true x ]
+    | x :: xs -> f false x :: map_last ~f xs
+
+  (* like [List.iter] except that it calls the function with
+     an additional argument to indicate whether we're iterating
+     over the last element of the list *)
+  let rec iter_last ~f l =
+    match l with
+    | [] -> ()
+    | [ a ] -> f true a
+    | a :: l ->
+        f false a;
+        iter_last ~f l
 end
 
 let ( @ ) = List.append