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Postings from October 2003
I'll change my earlier suggestion of how to handle this in Math::BigInt. I
suggest changing the current code in _root from:
# fit's into one Perl scalar, so result can be computed directly
$x->[0] = int( $x->[0] ** (1 / $n->[0]) );
to:
if ($x->[0] == 0) {
return 0;
}
# fits into one Perl scalar, so result can be computed directly
my $temp = $x->[0] ** (1 / $n->[0]);
my $a = int($temp);
my $b = int($temp + (($temp > 0) ? 0.5 : -0.5));
if ($a == $b) {
$x->[0] = $a;
} elsif (abs(($a**$n->[0]) - $x->[0]) > abs(($b**$n->[0]) - $x->[0])) {
$x->[0] = $b;
} else {
$x->[0] = $a;
}
return $x;
In other words, if adding 0.5 (equivalently, subtracting, if the result is
negative) will give a more arithmetically correct result after truncating, do
it; otherwise, don't. (It's likely that the same sort of thing would be
helpful for the _sqrt function.)
-Allen
--
Allen Smith http://cesario.rutgers.edu/easmith/
February 1, 2003 Space Shuttle Columbia
Ad Astra Per Aspera To The Stars Through Asperity
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