(* ========================================================================= *)
(* A POSSIBLY-INFINITE STREAM DATATYPE FOR ML *)
(* Copyright (c) 2001-2006 Joe Hurd, distributed under the BSD License *)
(* ========================================================================= *)
signature Stream =
sig
(* ------------------------------------------------------------------------- *)
(* The stream type *)
(* ------------------------------------------------------------------------- *)
datatype 'a stream = NIL | CONS of 'a * (unit -> 'a stream)
(* If you're wondering how to create an infinite stream: *)
(* val stream4 = let fun s4 () = Stream.CONS (4,s4) in s4 () end; *)
(* ------------------------------------------------------------------------- *)
(* Stream constructors *)
(* ------------------------------------------------------------------------- *)
val repeat : 'a -> 'a stream
val count : int -> int stream
val funpows : ('a -> 'a) -> 'a -> 'a stream
(* ------------------------------------------------------------------------- *)
(* Stream versions of standard list operations: these should all terminate *)
(* ------------------------------------------------------------------------- *)
val cons : 'a -> (unit -> 'a stream) -> 'a stream
val null : 'a stream -> bool
val hd : 'a stream -> 'a (* raises Empty *)
val tl : 'a stream -> 'a stream (* raises Empty *)
val hdTl : 'a stream -> 'a * 'a stream (* raises Empty *)
val singleton : 'a -> 'a stream
val append : 'a stream -> (unit -> 'a stream) -> 'a stream
val map : ('a -> 'b) -> 'a stream -> 'b stream
val maps : ('a -> 's -> 'b * 's) -> 's -> 'a stream -> 'b stream
val zipwith : ('a -> 'b -> 'c) -> 'a stream -> 'b stream -> 'c stream
val zip : 'a stream -> 'b stream -> ('a * 'b) stream
val take : int -> 'a stream -> 'a stream (* raises Subscript *)
val drop : int -> 'a stream -> 'a stream (* raises Subscript *)
(* ------------------------------------------------------------------------- *)
(* Stream versions of standard list operations: these might not terminate *)
(* ------------------------------------------------------------------------- *)
val length : 'a stream -> int
val exists : ('a -> bool) -> 'a stream -> bool
val all : ('a -> bool) -> 'a stream -> bool
val filter : ('a -> bool) -> 'a stream -> 'a stream
val foldl : ('a * 's -> 's) -> 's -> 'a stream -> 's
val concat : 'a stream stream -> 'a stream
val mapPartial : ('a -> 'b option) -> 'a stream -> 'b stream
val mapsPartial : ('a -> 's -> 'b option * 's) -> 's -> 'a stream -> 'b stream
(* ------------------------------------------------------------------------- *)
(* Stream operations *)
(* ------------------------------------------------------------------------- *)
val memoize : 'a stream -> 'a stream
val toList : 'a stream -> 'a list
val fromList : 'a list -> 'a stream
val toTextFile : {filename : string} -> string stream -> unit
val fromTextFile : {filename : string} -> string stream (* line by line *)
end