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Postings from December 2016
On Wed, 28 Dec 2016 21:07:53 -0800, zefram@fysh.org wrote:
> sisyphus1@optusnet.com.au wrote:
> > FWIW, on Windows (perl-5.25.7, MSWin32-x64-multi-thread) y1 and y2
> > are the
> > same as above, but y3 differs:
> ...
> > y3 =
> > 179769313486231570000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000.000000
>
> That's fucked up. Looks like it's libc's fault: sprintf() using a
> crap algorithm, converting to decimal with a fixed precision and then
> expanding that to the output precision, rather than actually
> converting
> to the output precision. Arguably we should implement our own float
> formatter to avoid this sort of problem.
I have a ticket open on using the netlib dtoa: https://rt.perl.org/Ticket/Display.html?id=122482
But am severely tuit-shortaged.
FWIW I tried adding
$x2 = '0x1.fffffffffffffp+1023';
$y4 = sprintf("%f", eval $x2);
$y5 = sprintf("%f", 0x1.fffffffffffffp+1023);
$y6 = sprintf("%a", DBL_MAX);
print "y4 = $y4\n";
print "y5 = $y5\n";
print "y6 = $y6\n";
and got
y4 = 179769313486231570814527423731704356798070567525844996598917476803157260780028538760589558632766878171540458953514382464234321326889464182768467546703537516986049910576551282076245490090389328944075868508455133942304583236903222948165808559332123348274797826204144723168738177180919299881250404026184124858368.000000
y5 = 179769313486231570814527423731704356798070567525844996598917476803157260780028538760589558632766878171540458953514382464234321326889464182768467546703537516986049910576551282076245490090389328944075868508455133942304583236903222948165808559332123348274797826204144723168738177180919299881250404026184124858368.000000
y6 = 0x1.fffffffffffffp+1023
which seems to indicate that the parsing of hexfp literals and the %a are okay (yay me).
> But anyway, that's unrelated to the input problem with which this
> ticket
> is concerned. Open a separate ticket if you want to pursue it.
>
> -zefram
---
via perlbug: queue: perl5 status: open
https://rt.perl.org/Ticket/Display.html?id=130423
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