CBFalconer wrote:
> I trust you meant 243.  You can also quickly multiply by 3 on very
> simple hardware, by shift and add twice.

yes thanks! 243
W4tch3r ‹•¿•›

Chris H wrote:
> In message 
> <b...@26g2000hsk.googlegroups.com>, 
> Tomás Ó hÉilidhe <t...@lavabit.com> writes
>> On May 13, 7:59 pm, Hans-Bernhard Bröker <HBBroe...@t-online.de>
>> wrote:
>>> > #define TOTAL_BITS_NEEDED (QUANTITY_CHUNKS * BITS_PER_CHUNK)
>>>
>>> Bad macro.  Parentheses missing around QUANTITY_CHUNKS and
>>> BITS_PER_CHUNK leave the code vulnerable to funny definitions of those
>>> constants (e.g. #define BITS_PER_CHUNK 2+3)  The same problem occurs
>>> repeatedly later on.
>>
>> You're confusing things. A macro is a self-contained, self-sufficient
>> entity. If I have a macro called QUANTITY_CHUNKS, then it should be
>> able to be used on its own without parentheses. If it needs
>> parentheses, then it is ill-formed.
> 
> Now you are running counter to most standards and guides for portability 
> and safety.

I suspect Chris misunderstands Tomas's point: that macros defining numeric 
expressions should have surrounding parentheses in the macro definition so 
they aren't required where they are used.  So

#define FOO (BAR+3)
  x = FOO+4;

rather than

#define FOO BAR+3
  x = (FOO)*4;

Hans-Bernard's point, of being paranoid of externally-defined macros and 
surrounding those with parentheses is good, of course.

-- 
Thad

CBFalconer wrote:
> You can also quickly multiply by 3 on very
> simple hardware, by shift and add twice.

Can't you multiply by three by shifting and adding *once*?