Re: __builtin_cpow((0,0),(0,0))

[Robert Dewar <dewar at adacore dot com>]

Paolo Carlini wrote:

> Interesting, thanks. The problem is, since the C standard is admittedly
> rather vague in this area, some implementation of the C library simply
> implement the basic formula (i.e., cexp(c*clog(z))) and don't deal *at all*
> with special cases. This leads *naturally* to (nan, nan).
> In other cases we are more "lucky", though.

Well this is a grotesquely inaccurate way of computing exponentiation
anyway unless you have a lot of extra guard bits for the intermediate
value, so any library that does this is brain dead anyway.
>    http://docs.hp.com/en/B2355-60103/cpow.3M.html
>
> Paolo.