Infer scalar types with let generalization

src/util.ml

@@ -0,0 +1,48 @@
+let assoc_opt key items =
+  let rec search = function
+    | [] -> None
+    | (candidate, value) :: rest -> if candidate = key then Some value else search rest
+  in
+  search items
+
+let hashtbl_find_opt table key = try Some (Hashtbl.find table key) with Not_found -> None
+
+let rec filter_map f = function
+  | [] -> []
+  | item :: rest -> (
+      match f item with
+      | Some value -> value :: filter_map f rest
+      | None -> filter_map f rest)
+
+let rec concat_map f = function
+  | [] -> []
+  | item :: rest -> f item @ concat_map f rest
+
+let rec list_init count f =
+  if count <= 0 then [] else f 0 :: list_init (count - 1) (fun index -> f (index + 1))
+
+let rec take count items =
+  if count <= 0 then []
+  else
+    match items with
+    | [] -> []
+    | item :: rest -> item :: take (count - 1) rest
+
+let rec drop count items =
+  if count <= 0 then items
+  else match items with [] -> [] | _ :: rest -> drop (count - 1) rest
+
+let contains value items = List.exists (fun item -> item = value) items
+
+let string_before_char text character =
+  match String.index_opt text character with
+  | Some index -> String.sub text 0 index
+  | None -> text
+
+let starts_with prefix text =
+  String.length text >= String.length prefix && String.sub text 0 (String.length prefix) = prefix
+
+let rec join separator = function
+  | [] -> ""
+  | [ single ] -> single
+  | item :: rest -> item ^ separator ^ join separator rest