refactor: make zippers return 'pop'ped elements

2 files changed, 14 insertions, 21 deletions

diff --git a/lib/zipper.ml b/lib/zipper.ml
index 413f365..5f3b37a 100644
--- a/lib/zipper.ml
+++ b/lib/zipper.ml
@@ -49,7 +49,9 @@ let goto n z =
   let step = if n < 0 then left else right in
   Fn.apply_n_times ~n:(abs n) step z
 
-let pop ?(n = 1) z = { z with after = Sequence.drop_eagerly z.after n }
+let pop ?(n = 1) z =
+  let a, b = Sequence.split_n z.after n in
+  (Sequence.of_list a, { z with after = b })
 
 let pop_before ?(n = 1) =
   let rec aux m z =
@@ -58,7 +60,10 @@ let pop_before ?(n = 1) =
   aux 0
 
 let pop_after ?(n = 1) z =
-  if right_length z < 2 then z else right z |> pop ~n |> left
+  if right_length z < 2 then (Sequence.empty, z)
+  else
+    let a, b = right z |> pop ~n in
+    (a, left b)
 
 let push x z = { z with after = Sequence.shift_right z.after x }
 let push_seq s z = { z with after = Sequence.append s z.after }
diff --git a/lib/zipper.mli b/lib/zipper.mli
index 0bbdf27..a300b12 100644
--- a/lib/zipper.mli
+++ b/lib/zipper.mli
@@ -106,30 +106,18 @@ val goto : int -> 'a zipper -> 'a zipper
     This involve [push]ing and [pop]ping elements before and after the
     cursor. *)
 
-val pop : ?n:int -> 'a zipper -> 'a zipper
+val pop : ?n:int -> 'a zipper -> 'a Sequence.t * 'a zipper
 (** Remove [n] elements at the cursor position (1 by default), if any,
-    and return the modified zipper. Calling [pop z],
+    and return them alongside the modified zipper. *)
 
-        - if [z] is [([3; 2; 1], [4; 5])], the result is [([3; 2; 1], [5])],
-        - if [z] is [([1; 2; 3], [])], the result is [([1; 2; 3], [])].
-    *)
-
-val pop_before : ?n:int -> 'a zipper -> 'a zipper
+val pop_before : ?n:int -> 'a zipper -> 'a Sequence.t * 'a zipper
 (** Remove [n] elements before the cursor (1 by default), if any, and
-    return the modified zipper. Calling [pop_before z],
-
-        - if [z] is [([3; 2; 1], [4; 5])], the result is [([2; 1], [4, 5])],
-        - if [z] is [([], [1; 2; 3])], the result is [([], [1; 2; 3])].
-    *)
+    return them alongside the modified zipper. *)
 
-val pop_after : ?n:int -> 'a zipper -> 'a zipper
+val pop_after : ?n:int -> 'a zipper -> 'a Sequence.t * 'a zipper
 (** Remove [n] elements after (and {b not} including) the cursor
-    (1 by default), if any, and return the modified zipper.
-    Calling [pop_after z],
-
-        - if [z] is [([3; 2; 1], [4; 5])], the result is [([3; 2; 1], [4])],
-        - if [z] is [([1; 2; 3], [4])], the result is [([1; 2; 3], [4])].
-    *)
+    (1 by default), if any, and return them alongside the modified
+    zipper. *)
 
 val push : 'a -> 'a zipper -> 'a zipper
 (** Insert an element at the cursor position.