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Re: Draft C bindings for IEEE 754-2008 part 4 now available
- From: "Joseph S. Myers" <joseph at codesourcery dot com>
- To: Vincent Lefevre <vincent+gcc at vinc17 dot org>
- Cc: Florian Weimer <fweimer at redhat dot com>, <gcc at gcc dot gnu dot org>, <libc-alpha at sourceware dot org>
- Date: Tue, 7 Jan 2014 16:45:49 +0000
- Subject: Re: Draft C bindings for IEEE 754-2008 part 4 now available
- Authentication-results: sourceware.org; auth=none
- References: <Pine dot LNX dot 4 dot 64 dot 1401041812480 dot 26743 at digraph dot polyomino dot org dot uk> <52CBD17A dot 50403 at redhat dot com> <Pine dot LNX dot 4 dot 64 dot 1401071428040 dot 18708 at digraph dot polyomino dot org dot uk> <Pine dot LNX dot 4 dot 64 dot 1401071446180 dot 18708 at digraph dot polyomino dot org dot uk> <20140107161937 dot GB984 at ypig dot lip dot ens-lyon dot fr>
On Tue, 7 Jan 2014, Vincent Lefevre wrote:
> On 2014-01-07 14:48:01 +0000, Joseph S. Myers wrote:
> > (Except that the IEEE 754 reduction operations - subclause 9.4 - return
> > "an implementation-defined approximation". But 9.2 is "Recommended
> > correctly rounded functions", e.g. exp and sin, for which the strictly
> > corresponding C functions are crexp and crsin.)
>
> Some of the reduction operations may be standardized with the
> correct rounding requirement in the future IEEE 1788 standard
> on interval arithmetic (even though I think that such operations
> do not belong to IEEE 1788), if it passes. In any case, they
> should also have their own correctly rounded version.
Sure, such a correctly rounded function is useful just like correctly
rounded versions of other functions. The proposed C bindings reserve cr*
names *only* for the specific functions listed in 9.2 where IEEE 754
recommends correctly rounded functions, not for other existing ISO C
functions (e.g. erf, tgamma) or functions added by the C bindings by
analogy with other IEEE 754 functions (e.g. tanpi), but I think correctly
rounded versions of other functions (with the same naming convention)
could reasonably be added to glibc if anyone wishes to implement them.
(I'd like to see GCC and glibc get full support for C99/C11 Annexes F and
G and the TS parts 1 and 4 at least, but given the amount of work involved
have no current plans to work on this.)
--
Joseph S. Myers
joseph@codesourcery.com