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[John Machin]

Yu-Xi Lim wrote:
> John Machin wrote:
>
> > How did you avoid division when testing for leap year?
> >
>
> Well, you're testing for a modulus, not really a division, so a nasty hack:
>
> def isleapyear(year):
> 	return not year&3
>
> works for 1901-2099.
>
> But programming like this causes all kinds of problems in future. Let's
> just hope there aren't too many 1MHz 8-bit computers left by then.

No, I meant a wider range, at least 1 <= year <= 9999. And it's not
only 1MHz 8-bit computers where non-nasty division/modulus avoidance
hacks can come in handy -- IIRC the millicode for the 32-bit HP PA-RISC
architecture takes 32 divide-step instructions to do an unsigned 32-bit
division. Division is intrinsically relatively slow on most boxes, but
division by a non-power-of-2 constant can be sped up, and so can "x %
constant == 0". 

Cheers,
John