🚀 go-pugleaf

In article <7516@apple.Apple.Com> lsr@apple.UUCP (Larry Rosenstein) writes:
>In article <4097@husc6.harvard.edu> olson@endor.UUCP (Eric K. Olson) writes:
>>In a recent article Richard Siegel writes:
>>>
>>>In LightspeedC, TRUE is one and FALSE is zero. 
>>
>>If memory serves me correctly, portions of the Mac OS use the highest
>>order (sign) bit for the state of a Boolean, a Pascalism, I think (forgive
>
>MPW Pascal uses 1 to mean TRUE and 0 for FALSE.  Inside Macintosh says that
>a BOOLEAN is represented in bit 0 (the low-order bit) of a byte.

However, it is my understanding that the Lisa Pascal compiler pushed _bytes_ 
on the stack for booleans.  A well-known fact about the 68000 is that it will
only push _words_ on the stack, even when you ask to push a byte.  Less
well-known is the fact that that word pushed will be byte-reversed!

Thus, when using a C compiler (whose minimum argument size is a word)
whenever you have to digest a boolean passed _from_ the toolbox you
will end up with a value of 256 for true and 0 for false since the C
compiler's code will only pop a word.  The Aztec C manual had a nice
little discussion about this, and recommended that you use the 'if
(fun())' and 'if (!fun())' method rather than 'if (fun()==TRUE)'.  

For added fun, the C convention is to use 1==TRUE, but if you have to
pass a boolean to the toolbox you can't use that since the toolbox
essentially uses 256 and 0!  Personally I prefer TRUE==(-1) and
FALSE==0, and never check explicitly for equality with either of these,
but use the fun() and !fun() method.  This gets me the best of both.

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