(***********************************************************************)
(*                                                                     *)
(*                             Ocaml                                   *)
(*                                                                     *)
(*        Daniel de Rauglaudre, projet Cristal, INRIA Rocquencourt     *)
(*                                                                     *)
(*  Copyright 1997 Institut National de Recherche en Informatique et   *)
(*  en Automatique.  All rights reserved.  This file is distributed    *)
(*  under the terms of the GNU Library General Public License.         *)
(*                                                                     *)
(***********************************************************************)

(* $Id: stream.mli,v 1.18 2000/04/03 01:57:44 garrigue Exp $ *)

(* Module [Stream]: streams and parsers *)

type 'a t
        (* The type of streams holding values of type ['a]. *)

exception Failure;;
        (* Raised by parsers when none of the first components of the stream
           patterns is accepted. *)
exception Error of string;;
        (* Raised by parsers when the first component of a stream pattern is
           accepted, but one of the following components is rejected. *)

(** Stream builders *)
(* Warning: these functions create streams with fast access; it is illegal
   to mix them with streams built with [[< >]]; would raise [Failure]
   when accessing such mixed streams. *)

val from : (int -> 'a option) -> 'a t;;
        (* [Stream.from f] returns a stream built from the function [f].
           To create a new stream element, the function [f] is called with
           the current stream count. The user function [f] must return either
           [Some <value>] for a value or [None] to specify the end of the
           stream. *)
val of_list : 'a list -> 'a t;;
        (* Return the stream holding the elements of the list in the same
           order. *)
val of_string : string -> char t;;
        (* Return the stream of the characters of the string parameter. *)
val of_channel : in_channel -> char t;;
        (* Return the stream of the characters read from the input channel. *)

(** Stream iterator *)

val iter : f:('a -> unit) -> 'a t -> unit;;
        (* [Stream.iter f s] scans the whole stream s, applying function [f]
           in turn to each stream element encountered. *)

(** Predefined parsers *)

val next : 'a t -> 'a;;
        (* Return the first element of the stream and remove it from the
           stream. Raise [Stream.Failure] if the stream is empty. *)
val empty : 'a t -> unit;;
        (* Return [()] if the stream is empty, else raise [Stream.Failure]. *)

(** Useful functions *)

val peek : 'a t -> 'a option;;
        (* Return [Some] of "the first element" of the stream, or [None] if
           the stream is empty. *)
val junk : 'a t -> unit;;
        (* Remove the first element of the stream, possibly unfreezing
           it before. *)
val count : 'a t -> int;;
        (* Return the current count of the stream elements, i.e. the number
           of the stream elements discarded. *)

val npeek : int -> 'a t -> 'a list;;
        (* [npeek n] returns the list of the [n] first elements of
           the stream, or all its remaining elements if less than [n]
           elements are available. *)

(*--*)

(*** For system use only, not for the casual user *)

val iapp : 'a t -> 'a t -> 'a t;;
val icons : 'a -> 'a t -> 'a t;;
val ising : 'a -> 'a t;;

val lapp : (unit -> 'a t) -> 'a t -> 'a t;;
val lcons : (unit -> 'a) -> 'a t -> 'a t;;
val lsing : (unit -> 'a) -> 'a t;;

val sempty : 'a t;;
val slazy : (unit -> 'a t) -> 'a t;;

val dump : ('a -> unit) -> 'a t -> unit;;
