Path: utzoo!attcan!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!van-bc!rsoft!mindlink!a665
From: a665@mindlink.UUCP (Anthon Pang)
Newsgroups: comp.lang.modula2
Subject: Re: Bitwise EXOR
Message-ID: <3356@mindlink.UUCP>
Date: 29 Sep 90 03:37:26 GMT
Organization: MIND LINK! - British Columbia, Canada
Lines: 32

Herman.Stevens@p21701.f601.n292.z2.fidonet.org writes:
> I am a beginner with Modula-II. I work on an Amiga with the M2Amiga
> compiler. I fail to see how I can do a bitwise EXOR, something you
> can easily write in C as :
> 
>          tmpbuf[i] = inbuf[i]^key[kp]
> 
> Can someone help me on this ?

I think the following work...

For booleans:

   x := ( a OR b) AND (NOT (a AND b));

and for other stuff (using sufficient type transfer):

   TYPE
     longbs = SET OF [0..31]; (* LONG WORD BITSET *)

   PROCEDURE XOR ( x, y: longbs ) : longbs;
     CONST
       allset = longbs{0..31};
     BEGIN
       RETURN (x + y) * (allset - (x * y));
     END XOR;

For the latter case, your example would translate (roughly) to:
tmpbuf[i] := LONGCARD( XOR(longbs(inbuf[i]), longbs(key[kp])));
assuming tmpbuf is an ARRAY of LONGCARD.  Change "LONGCARD" to "CARDINAL" and
"31" to "15"...and it should work for word size (16 bit) values as well (ie on
the Amiga).