[Issue 3171] % not implemented correctly for floats

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=3171


Don <clugdbug at yahoo.com.au> changed:

           What    |Removed                     |Added
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                 CC|                            |clugdbug at yahoo.com.au




--- Comment #2 from Don <clugdbug at yahoo.com.au>  2009-07-14 01:49:30 PDT ---
(In reply to comment #1)
> As to why the code generator doesn't use FPREM1 instead of FPREM, there's the
> following comment: "We don't use fprem1 because for some inexplicable
> reason we get -5 when we do _modulo(15, 10)"
> 
> This could be a bug in older CPUs.

It isn't a bug. That's what the IEEE remainder specifies.
Note that C's fmod is NOT the same as IEEE remainder.

15/10 = 1.5, so there's a choice of n == 1 or n==2. The standard specifies even
n in such cases, so r == a - b*n == 15 - 2*10 == -5.

That's kind of... weird, highly non-intuitive, and not terribly useful. I'm
pretty sure that that behaviour would be unpopular.

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