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Postings from January 2005
On Sun, Dec 19, 2004 at 03:01:19PM -0800, Yitzchak Scott-Thoennes <sthoenna@efn.org> wrote: > On Sun, Dec 19, 2004 at 03:22:54PM -0500, John Peacock <jpeacock@rowman.com> wrote: > > Binary "<=>" returns -1, 0, or 1 depending on whether the left > > argument is numerically less than, equal to, or greater than the right > > argument. If your platform supports NaNs (not-a-numbers) as numeric > > -values, using them with "<=>" (or any other numeric comparison) > > -returns undef. > > +values, using them with "<=>" returns undef. NaN is not "<", "==", ">", > > +"<=" or ">=" anything (even NaN), so those 5 return false. NaN != NaN > > +returns true, as does NaN != anything else. If your platform doesn't > > +support NaNs then NaN is just a string with numeric value 0. > > + > > + perl -le '$a = NaN; print "No NaN support here" if $a == $a' > > + perl -le '$a = NaN; print "NaN support here" if $a != $a' > > Unfortunately it seems the part to suppress numeric warnings for > inf/nan-looking strings is there, but not the part to actually make > them be non-zero numbers. Don't know if this was always the case, or > if the code to make the above snippet work was once present but now > broken. Aha! In 5.6.x, perl uses the libc atof/strtold/atofl to parse numbers; at some point in 5.8.x it was changed to use a replacement in numeric.c (unless on Unicos or configured with -Accflags=-DUSE_PERL_ATOF=0). And the numeric.c atof doesn't support nan/inf.