Rewrite simple option pattern matching with Option.fold.

Turn simple pattern matching involding option types into
one-liner using Option.fold.

examples/inmemory_zipstore.ml

@@ -54,13 +54,11 @@ end = struct
           | Ok s -> s
 
     let get_partial_values t key ranges =
-      get t key >>= fun data ->
+      get t key >>| fun data ->
       let size = String.length data in
-      ranges |> Lwt_list.map_p @@ fun (offset, len) ->
-      Deferred.return
-      (match len with
-      | None -> String.sub data offset (size - offset)
-      | Some l -> String.sub data offset l)
+      ranges |> List.map @@ fun (ofs, len) ->
+      let f v = String.sub data ofs v in
+      Option.fold ~none:(f (size - ofs)) ~some:f len
 
     let list t =
       Deferred.return @@ Zipc.fold

examples/readonly_zipstore.ml

@@ -53,10 +53,9 @@ end = struct
     let get_partial_values t key ranges =
       get t key >>= fun data ->
       let size = String.length data in
-      ranges |> Eio.Fiber.List.map @@ fun (offset, len) ->
-      match len with
-      | None -> String.sub data offset (size - offset)
-      | Some l -> String.sub data offset l
+      ranges |> Eio.Fiber.List.map @@ fun (ofs, len) ->
+      let f v = String.sub data ofs v in
+      Option.fold ~none:(f (size - ofs)) ~some:f len
 
     let list t =
       Zip.entries t |> Eio.Fiber.List.filter_map @@ function

zarr-sync/src/storage.ml

@@ -34,13 +34,10 @@ module FilesystemStore = struct
         (fun ic ->
           let size = In_channel.length ic |> Int64.to_int in
           List.map
-            (fun (rs, len) ->
-              let len' =
-                match len with
-                | Some l -> l
-                | None -> size - rs in
-              In_channel.seek ic @@ Int64.of_int rs;
-              Option.get @@ In_channel.really_input_string ic len') ranges)
+            (fun (ofs, len) ->
+              In_channel.seek ic @@ Int64.of_int ofs;
+              let l = Option.fold ~none:(size - ofs) ~some:Fun.id len in 
+              Option.get @@ In_channel.really_input_string ic l) ranges)
 
     let set t key value =
       let filename = key_to_fspath t key in

zarr/src/storage/memory.ml

@@ -47,14 +47,12 @@ module Make (Deferred : Types.Deferred) = struct
     if not success then erase_prefix t pre else Deferred.return_unit
 
   let get_partial_values t key ranges =
-    get t key >>= fun v ->
+    get t key >>| fun v ->
     let size = String.length v in
-    Deferred.return @@
     List.fold_left
       (fun acc (ofs, len) ->
-        match len with
-        | None -> String.sub v ofs (size - ofs) :: acc
-        | Some l -> String.sub v ofs l :: acc) [] @@ List.rev ranges
+        let f x = String.sub v ofs x :: acc in
+        Option.fold ~none:(f (size - ofs)) ~some:f len) [] @@ List.rev ranges
 
   let rec set_partial_values t key ?(append=false) rv =
     let f = if append then fun acc (_, v) -> acc ^ v else

zarr/src/storage/storage.ml

@@ -33,9 +33,8 @@ module Make (Io : Types.IO) = struct
     | false ->
       let k = GroupNode.to_metakey node in
       set t k GroupMetadata.(update_attributes default attrs |> encode) >>= fun () ->
-      match GroupNode.parent node with
-      | None -> Deferred.return_unit
-      | Some n -> create_group t n
+      GroupNode.parent node
+      |> Option.fold ~none:Deferred.return_unit ~some:(create_group t)
 
   let create_array
     ?(sep=`Slash) ?(dimension_names=[]) ?(attributes=`Null)

zarr/src/util.ml

@@ -17,9 +17,7 @@ module ArrayMap = struct
   end)
 
   let add_to_list k v map =
-    update k (function
-      | None -> Some [v]
-      | Some l -> Some (v :: l)) map
+    update k (Option.fold ~none:(Some [v]) ~some:(fun l -> Some (v :: l))) map
 end
 
 module Result_syntax = struct
@@ -106,6 +104,4 @@ let rec create_parent_dir fn perm =
   end
 
 let sanitize_dir dir =
-  match Filename.chop_suffix_opt ~suffix:"/" dir with
-  | None -> dir
-  | Some d -> d
+  Option.fold ~none:dir ~some:Fun.id @@ Filename.chop_suffix_opt ~suffix:"/" dir