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(*pp camlp4o *)
(* arch-tag: BNF support code
Copyright (C) 2004 John Goerzen <jgoerzen@complete.org>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*)
open List;;
open Stream;;
class ['a] lazyStream (parentstream: 'a Stream.t) =
object (self)
val mutable cache = []
val mutable cstream = parentstream
val mutable lastconsume = 0
initializer
cstream <- Stream.from self#nth_item
method nth_item n =
let oldlen = length cache in
if n < oldlen then
Some (nth cache n)
else begin
let newval = npeek (n+1) parentstream in
if (length newval) != (n+1) then
None
else begin
cache <- newval;
Some (nth newval n);
end;
end;
method next_item = self#nth_item (length cache)
(*
method consumeall =
let rec thefunc () = match cache with
[] -> ()
| x::xs -> junk parentstream; cache <- xs; thefunc()
in
thefunc ()
method reset = cache <- []
*)
method consume_stream =
let n_to_consume = count cstream - lastconsume in
let rec consumeit n = match n with
0 -> ()
| x -> junk parentstream; (* cache <- tl cache; *) consumeit (x -1) in
consumeit n_to_consume;
lastconsume <- count cstream;
(*
method to_stream = let rec thefunc () = match self#next_item with
None -> [< >]
| Some item -> [< 'item; thefunc() >]
in thefunc ()
*)
method to_stream = cstream
end;;
|
