feat(zipper): add option to not move past last element when moving right

1 files changed, 16 insertions, 10 deletions

diff --git a/lib/zipper.mli b/lib/zipper.mli
index a300b12..0481cfe 100644
--- a/lib/zipper.mli
+++ b/lib/zipper.mli
@@ -46,8 +46,10 @@ val focus_or : default:'a -> 'a zipper -> 'a
 val is_far_left : 'a zipper -> bool
 (** Return whether the cursor is at the beginning of the zipper. *)
 
-val is_far_right : 'a zipper -> bool
-(** Return whether the cursor is at the end of the zipper. *)
+val is_far_right : ?by_one:bool -> 'a zipper -> bool
+(** Return whether the cursor is at the end of the zipper.
+    If [by_one] is [true], the cursor is considered at the far right
+    even when pointing {b to} the last element of the sequence. *)
 
 val is_empty : 'a zipper -> bool
 (** Return whether the zipper is empty. *)
@@ -79,26 +81,30 @@ val left_while : ('a -> bool) -> 'a zipper -> 'a zipper
 val far_left : 'a zipper -> 'a zipper
 (** Move the cursor to the left, as much as possible. *)
 
-val right : 'a zipper -> 'a zipper
-(** Move the cursor one step to the right, if possible.
+val right : ?by_one:bool -> 'a zipper -> 'a zipper
+(** Move the cursor one step to the right, if possible. If [by_one] is
+    [true], the cursor won't move past the last element.
     Calling [right z],
 
         - if [z] is [([3; 2; 1], [4; 5])], the result is [([4; 3; 2; 1], [5])], 
         - if [z] is [([1; 2; 3], [])], the result is [([1; 2; 3], [])].
     *)
 
-val right_while : ('a -> bool) -> 'a zipper -> 'a zipper
+val right_while : ?by_one:bool -> ('a -> bool) -> 'a zipper -> 'a zipper
 (** [right_while f z] moves the cursor in [z] to the right as long as
     the predicate [f] is [true] when applied to the focus, or the right
-    end of the zipper is reached. *)
+    end of the zipper is reached. If [by_one] is [true], the cursor won't
+    move past the last element. *)
 
-val far_right : 'a zipper -> 'a zipper
-(** Move the cursor to the right, as much as possible. *)
+val far_right : ?by_one:bool -> 'a zipper -> 'a zipper
+(** Move the cursor to the right, as much as possible. If [by_one] is
+    [true], the cursor won't move past the last element.*)
 
-val goto : int -> 'a zipper -> 'a zipper
+val goto : ?by_one:bool -> int -> 'a zipper -> 'a zipper
 (** Move the cursor to a specific (absolute) position in the zipper.
     Depending on the current position, it either moves the cursor
-    forward or backwards, without crossing the zipper boundaries. *)
+    forward or backwards, without crossing the zipper boundaries. If
+    [by_one] is [true], the cursor won't move past the last element. *)
 
 (** {1 Changes at the cursor} *)