Re: floor, ceil, trunc, round, minus zero, and alpha

[Bruno Haible]

Eric Blake wrote:
> >   - are marked as [MX] in POSIX [1][2][3][4], that is, an optional feature
> >     not contained in ISO C 99,
> 
> [MX] means that the behavior is required on platforms that claim IEC
> 60559 conformance (aka IEEE 754 format); it means that you fully
> implement the otherwise-optional Appendix F of the C99 standard.

I see. Thanks for correcting me.

Regarding DEC Alpha platforms, I don't think they are 100% IEEE 754 + 854
compliant, because the hardware designers took some shortcuts regarding
the exception handling, in order to implement the floating-point operations
in a single CPU cycle.

> >   - make little sense for 'ceil' from a mathematical point of view:
> >     ceil is a monotonically increasing function but POSIX wants
> >     ceil(-0.5) = 0.0 and ceil(-0.0) = -0.0,
> 
> I'll raise that point with the Austin group.

Given that the annex section F.9.6.1 in ISO C99 already specifies this
behaviour, I don't think the Austin group will deviate from that.

Bruno