succ_stream.sa

 
---------------------------> Sather 1.1 source file <--------------------------
-- Successor stream
-- Author: Benedict A. Gomes <gomes@samosa.ICSI.Berkeley.EDU>
-- Copyright (C) 1995, International Computer Science Institute
-- $Id: succ_stream.sa,v 1.1 1996/07/13 06:48:51 gomes Exp $
--
-- COPYRIGHT NOTICE: This code is provided WITHOUT ANY WARRANTY
-- and is subject to the terms of the SATHER LIBRARY GENERAL PUBLIC
-- LICENSE contained in the file: Sather/Doc/License of the
-- Sather distribution. The license is also available from ICSI,
-- 1947 Center St., Suite 600, Berkeley CA 94704, USA.


abstract class $SUCC_STREAM{NTP} 
abstract class $SUCC_STREAM{NTP} is
   -- An abstraction that specifies a generator of successive 
   -- unique values of type NTP
   
   next: NTP;
   -- Return the next unique value
   
end;


class INT_STREAM < $SUCC_STREAM{INT} 
class INT_STREAM < $SUCC_STREAM{INT} is
   -- Yield a stream of successive integers

   private attr val: INT;
   
   create(start_val: INT): SAME is
      -- Return a new integer stream whose next yielded
      -- value will be "start_val"
      res ::= new;
      res.val := start_val;
      return res;
   end;
   
   next: INT is
      -- Yield the next integer in this stream
      -- Wrap around is not permitted in this kind of integer stream
      res ::= val;
      assert val /= INT::maxint;
      val := val+1;
      return res;
   end;
   
   
   next!: INT is
      -- Keep yielding successive integers. 
      -- Will quit at maxint - 1
      if val = INT::maxint then quit end;
      yield next;
   end;
   
end;