Re: Bitwise XOR?

["Robert I. Eachus" <rieachus@comcast.net>]

Beard, Frank Randolph CIV wrote:
> You don't even need the Unchecked_Conversion.
> 
> The following should work:
> 
>   function "xor"(Left,Right : in Integer) return Integer is
>     pragma inline("xor");
>     type Int_As_Mod is mod 2 ** Integer'size;
>   begin
>     return Integer( Int_As_Mod(Left) XOR Int_As_Mod(Right) );
>   end "xor";
> 
> Theoretically, Unchecked_Conversion should be faster I guess.
> Is that why you chose it, or did you do some timing tests
> that showed a noticeable difference?

First, the Unchecked_Conversion is correct.  The above code will not do 
what you expect with negative numbers, it will raise an exception.  The 
Unchecked_Conversion will not only prevent the "unnecessary" check, but 
will also be faster.

-- 
                                                     Robert I. Eachus

"Quality is the Buddha. Quality is scientific reality. Quality is the 
goal of Art. It remains to work these concepts into a practical, 
down-to-earth context, and for this there is nothing more practical or 
down-to-earth than what I have been talking about all along...the repair 
of an old motorcycle."  -- from Zen and the Art of Motorcycle 
Maintenance by Robert Pirsig