Path: utzoo!attcan!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!rice!titan.rice.edu!preston
From: preston@titan.rice.edu (Preston Briggs)
Newsgroups: comp.lang.modula2
Subject: Re: Bitwise EXOR
Message-ID: <1990Sep30.133717.7936@rice.edu>
Date: 30 Sep 90 13:37:17 GMT
References: <1230@cluster.cs.su.oz.au>
Sender: news@rice.edu (News)
Organization: Rice University, Houston
Lines: 36

In article <1230@cluster.cs.su.oz.au> steve@cluster.cs.su.oz (Stephen Russell) writes:
>Herman Stevens asks:
>>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 ?
>
>It ain't as simple as in C (but then neither are bit-ands and ors). Try
>using the symmetric set difference operator by casting. Something
>like this might work:
>
>	tmpbuf[i] := CARDINAL(BITSET(inbuf[i]) / BITSET(key[kp]))

Well, if you want to fiddle bits, use BITSETs in the first place.
Then, assuming you've declared all your variables as arrays
of BITSET, you simply write

	tmpbuf[i] := inbuf[i] / key[kp]

I think "symmetric set difference" is a rather unhelpful name,
but perhaps it's more common in Europe.

Note also that the BITSET idea is handy for testing and setting
particular bits.

	IF 2 IN key[kp] THEN ...

or

	tmpbuf[i] := key[kp] + {5, 7}

-- 
Preston Briggs				looking for the great leap forward
preston@titan.rice.edu