more functions in CCList.Zipper

src/core/CCList.ml

@@ -833,10 +833,18 @@ module Zipper = struct
     | x::l, r -> l, x::r
     | [], r -> [], r
 
+  let left_exn = function
+    | x::l, r -> l, x::r
+    | [], _ -> invalid_arg "zipper.left_exn"
+
   let right = function
     | l, x::r -> x::l, r
     | l, [] -> l, []
 
+  let right_exn = function
+    | l, x::r -> x::l, r
+    | _, [] -> invalid_arg "zipper.right_exn"
+
   let modify f z = match z with
     | l, [] ->
         begin match f None with
@@ -874,7 +882,11 @@ module Zipper = struct
 
   let drop_before (_, r) = [], r
 
-  let drop_after (l, _) = l, []
+  let drop_after (l, r) = match r with
+    | [] -> l, []
+    | x :: _ -> l, [x]
+
+  let drop_after_and_focused (l, _) = l, []
 end
 
 (** {2 References on Lists} *)

src/core/CCList.mli

@@ -331,9 +331,19 @@ module Zipper : sig
   val left : 'a t -> 'a t
   (** Go to the left, or do nothing if the zipper is already at leftmost pos *)
 
+  val left_exn : 'a t -> 'a t
+  (** Go to the left, or
+      @raise Invalid_argument if the zipper is already at leftmost pos
+      @since NEXT_RELEASE *)
+
   val right : 'a t -> 'a t
   (** Go to the right, or do nothing if the zipper is already at rightmost pos *)
 
+  val right_exn : 'a t -> 'a t
+  (** Go to the right, or
+      @raise Invalid_argument if the zipper is already at rightmost position
+      @since NEXT_RELEASE *)
+
   val modify : ('a option -> 'a option) -> 'a t -> 'a t
   (** Modify the current element, if any, by returning a new element, or
       returning [None] if the element is to be deleted *)
@@ -365,8 +375,20 @@ module Zipper : sig
       @since NEXT_RELEASE *)
 
   val drop_after : 'a t -> 'a t
-  (** Drop every element on the "right" (calling {!right} then will do nothing).
+  (** Drop every element on the "right" (calling {!right} then will do nothing),
+      keeping the focused element, if any.
       @since NEXT_RELEASE *)
+
+  val drop_after_and_focused : 'a t -> 'a t
+  (** Drop every element on the "right" (calling {!right} then will do nothing),
+      {i including} the focused element if it is present.
+      @since NEXT_RELEASE *)
+
+  (*$=
+    ([1], [2]) (Zipper.drop_after ([1], [2;3]))
+    ([1], []) (Zipper.drop_after ([1], []))
+    ([1], []) (Zipper.drop_after_and_focused ([1], [2;3]))
+  *)
 end
 
 (** {2 References on Lists}