Re: support for bitwise comparison of floats

[Eric Blake]

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According to Bruno Haible on 3/25/2007 4:54 AM:
> Eric Blake wrote:
>> You can also assume IEEE rules, and compare against signed infinity:
>> 1 / +0. => +infinity
>> 1 / -0. => -infinity
> 
> Nice trick :-)

Thanks for correcting my typo; which I realized after I sent my other
message. :)

> 
> But here you depend on the IEEE rules for exceptions upon division by zero.
>   - On Alpha processors, division by zero (and even overflow!) leads to a 
> SIGFPE
>     signal by default. And it requires the use of a system call to change
>     the FP exceptions control mask (the <fenv.h> routines in glibc >= 2.1,
>     the __setfpucw function in glibc 2.0). memcmp is certainly much cheaper.

Raw operations on bits is much faster than actual floating point in a
number of cases; as you have noted, the problem is the portability in
detecting where the raw bits are.  Your method appears fine to me.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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