From 121a6a376209de3f5a9474bf03721e2032a73e01 Mon Sep 17 00:00:00 2001
From: Marc Coquand <marc@mccd.space>
Date: Mon, 13 May 2024 11:00:47 -0500
Subject: initial commit

---
 lib/zipper.ml | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)
 create mode 100644 lib/zipper.ml

(limited to 'lib/zipper.ml')

diff --git a/lib/zipper.ml b/lib/zipper.ml
new file mode 100644
index 0000000..37e14de
--- /dev/null
+++ b/lib/zipper.ml
@@ -0,0 +1,22 @@
+type zipper =
+  { above : string list
+  ; selected : string
+  ; below : string list
+  }
+
+let up (zipper : zipper) =
+  match zipper.above with
+  | [] -> zipper
+  | a :: rest -> { above = rest; selected = a; below = zipper.selected :: zipper.below }
+
+
+let down (zipper : zipper) =
+  match zipper.below with
+  | [] -> zipper
+  | a :: rest -> { below = rest; selected = a; above = zipper.selected :: zipper.above }
+
+
+let selected zipper = zipper.selected
+
+let to_array zipper =
+  List.concat [ zipper.above; [ zipper.selected ]; zipper.below ] |> Array.of_list
-- 
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