Copyright 1996-2003 John D. Polstra.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgment:
* This product includes software developed by John D. Polstra.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* $Id: Merger.mg.html,v 1.3 2010-04-29 17:20:02 wagner Exp $
GENERIC MODULE Merger(Elem);
REVEAL
T = Public BRANDED OBJECT
curA, curB: Elem.T;
wantA, wantB := TRUE;
OVERRIDES
compare := Compare;
next := Next;
END;
PROCEDURE Compare(<*UNUSED*> self: T; READONLY a, b: Elem.T): [-1..1] =
BEGIN
RETURN Elem.Compare(a, b);
END Compare;
PROCEDURE Next(self: T; VAR a, b: Elem.T): BOOLEAN RAISES ANY =
VAR
cmp: [-1..1];
BEGIN
IF self.wantA THEN
self.curA := self.getA();
self.wantA := FALSE;
END;
IF self.wantB THEN
self.curB := self.getB();
self.wantB := FALSE;
END;
IF self.curA # NIL OR self.curB # NIL THEN
IF self.curA = NIL THEN (* End of sequence A *)
cmp := 1;
ELSIF self.curB = NIL THEN (* End of sequence B *)
cmp := -1;
ELSE
cmp := self.compare(self.curA, self.curB);
END;
IF cmp <= 0 THEN
a := self.curA;
self.wantA := TRUE;
ELSE
a := NIL;
END;
IF cmp >= 0 THEN
b := self.curB;
self.wantB := TRUE;
ELSE
b := NIL;
END;
RETURN TRUE;
END;
RETURN FALSE;
END Next;
BEGIN
END Merger.