🚀 go-pugleaf

In article <1996Feb8.114044.15072@ucl.ac.uk> Chris Austin,
zcaccau@cs.ucl.ac.uk writes:
>Is there an XOR function in Topspeed Modula-2 V3.something.  I want to be
>able to XOR either 2 cardinals or 2 BITSETs, so if there isn't a function,
>what is the best way to implement it.  I need speed, not simplicity, as this
>is for graphics routines.
>

I just yesterday needed that to create a XOR checksum required for the
Windows "placeable" Meta-file header!

Low-level tricks like that can be done using SET operations. XOR is "/"
which means for A, B and C CARDINALs:

  "C = A XOR B" <=> C := CARDINAL( BITSET(A) / BITSET(B) );

Check out the "TopSpeed Language Tutorial" on SETs in case I remembered
it wrong. TopSpeed also has a "bitwise boolean operator" pragma that
sometimes
can be handy but which of course is nonportable.

.......................................................................
Bengt-Inge Dalenback
at:                                     and:
   Department of Applied Acoustics         CATT
   Chalmers University of Technology       (Software for room acoustic 
   Gothenburg, SWEDEN                      prediction and auralization)
   e-mail: bid@ta.chalmers.se              e-mail: catt@netg.se