In perl.git, the branch blead has been updated <http://perl5.git.perl.org/perl.git/commitdiff/c53cd05fe82f107ce9fb3b4a57e5d5d016ffc1f5?hp=c1521c2084bc5cbe818891777547f7d3e204146c>
- Log ----------------------------------------------------------------- commit c53cd05fe82f107ce9fb3b4a57e5d5d016ffc1f5 Author: Jarkko Hietaniemi <[email protected]> Date: Wed Jan 28 07:23:43 2015 -0500 infnan: even more comment tweaks ----------------------------------------------------------------------- Summary of changes: numeric.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/numeric.c b/numeric.c index 72676a4..d5c422f 100644 --- a/numeric.c +++ b/numeric.c @@ -741,17 +741,23 @@ Perl_grok_infnan(pTHX_ const char** sp, const char* send) * a single UV cannot contain all the possible * NaN payload bits. There would need to be * some more generic syntax than "nan($uv)". + * * Issues to keep in mind: * * (1) In most common cases there would * not be an integral number of bytes that * could be set, only a certain number of bits. - * For example for the common NVSIZE == UVSIZE - * there is room for 52 bits in the payload, - * but one bit is commonly reserved for the - * signal/quiet bit, so 51 bits. For the - * x86 80-bit doubles there would be 62 bits, - * and so forth. + * For example for the common case of + * NVSIZE == UVSIZE == 8 there is room for 52 + * bits in the payload, but the most significant + * bit is commonly reserved for the + * signaling/quiet bit, leaving 51 bits. + * Furthermore, the C99 nan() is supposed + * to generate quiet NaNs, so it is doubtful + * whether it should be able to generate + * signaling NaNs. For the x86 80-bit doubles + * (if building a long double Perl) there would + * be 62 bits (s/q bit being the 63rd). * * (2) Endianness of the payload bits. If the * payload is specified as an UV, the low-order -- Perl5 Master Repository
