Data update

Task/Queue-Definition/OCaml/queue-definition-1.ml

@@ -0,0 +1,20 @@
+module FIFO : sig
+  type 'a fifo
+  val empty: 'a fifo
+  val push: fifo:'a fifo -> item:'a -> 'a fifo
+  val pop: fifo:'a fifo -> 'a * 'a fifo
+  val is_empty: fifo:'a fifo -> bool
+end = struct
+  type 'a fifo = 'a list * 'a list
+  let empty = [], []
+  let push ~fifo:(input,output) ~item = (item::input,output)
+  let is_empty ~fifo =
+    match fifo with
+    | [], [] -> true
+    | _ -> false
+  let rec pop ~fifo =
+    match fifo with
+    | input, item :: output -> item, (input,output)
+    | [], [] -> failwith "empty fifo"
+    | input, [] -> pop ([], List.rev input)
+end