Re: [gentoo-science] question about signbit

[Darren Dale <dd55@cornell.edu>]

On Saturday 22 October 2005 5:05 pm, Marco Matthies wrote:
> Darren Dale wrote:
> > On my system, SciPy's signbit function reports that the sign bit is not
> > set for any number, positive or negative. Could someone here help me
> > understand how to test the libc signbit function? I have to admit I have
> > no experience with C programming.
>
> Hi Darren,
>
> the signbit fuction is actually a macro (as the manpage says) defined in
> math.h that in turn calls the right inline function (for the type
> needed) which is defined in mathinline.h --- so as far as i can see,
> libc should not be involved, only header files. I have attached a small
> example below on how to use the function. Please note the use of
> -std=c99 (you may also use -std=gnu99) as the macro is only activated
> when in C99 mode and gcc's default mode is C89 ("ANSI C"). If you're
> interested in the differences between the two standards the wikipedia
> entry on c has some info:
> http://en.wikipedia.org/wiki/C_programming_language

Hi Marko,

Thank you for your thoughtful and informative response. I have learned a few 
things.

Your test shows that signbit is working just fine on my system. I will discuss 
my results with the SciPy folks.

Thanks again,
Darren
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