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 jos...@codesourcery.com
