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Postings from October 2003
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Moin all,
I am now between a rock and a hard place:
POSIX::floor () converts the 81 as result to 80, as does int().
sprinf("%.0f"), OTOH, converts this fine to 81, but it
fails for things like 9.91234 - this should be truncated to 9, but sprintf
rounds it to 10.
Here is a case where the new sprintf("%.0f") fails, but the former int()
works:
# perl -Mbigint -le 'print 9999->broot()'
99
# perl -Ilib -Mbigint -le 'print 9999->broot()'
100
And here is one where the old one fails, but the new one works:
# perl -Mbigint -le 'print +(81 ** 3)->broot(3)'
80
# perl -Ilib -Mbigint -le 'print +(81 ** 3)->broot(3)'
81
:-(
Hm, Paul Johnson <paul@pjcj.net> wrote:
>Because (81 ** 3) ** (1/3) != 81
>
>$ perl -le 'print ((81 ** 3) ** (1/3) != 81)'
>1
>
>$ perl -MPOSIX -le '$a = (81 ** 3) ** (1/3); print join(" ", $a, int ($a),
>POSIX::floor($a), sprintf("%f",$a), sprintf("%.20f",$a), sprintf
>("%.0f",$a))'
>81 80 80 81.000000 80.99999999999998578915 81
Argl.
So, if I first round the result to 8 digits after the ".", I get rid of the
small variances, and can the truncate the result properly? Or should I just
add 0.5? Decisions....
$x->[0] = int ( sprintf ("%.8f", $x->[0] ** (1 / $n->[0]) ) );
This seems to work for both cases on my system.....
Best wishes,
Tels
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