Pentium math???

by desertrat (Acolyte)

on Apr 25, 2012 at 19:14 UTC ( #967148=perlquestion: print w/ replies, xml )

Need Help??

desertrat has asked for the wisdom of the Perl Monks concerning the following question:

Consider the simple code:

#!/usr/bin/perl
use strict;
use warnings;
my $i = 2456043.499992;
my $j = int($i);
my $k = $i-$j;
print "$i - $j == $k\n";
exit;
[download]

Which gives me the nonsensical results:

dbdev2:~ johnson$ perl test

2456043.499992 - 2456043 == 0.499991999939084

Huh?

Comment on Pentium math??? Download Code
Re: Pentium math??? by toolic (Chancellor) on Apr 25, 2012 at 19:19 UTC
perlfaq4 ... Why am I getting long decimals (eg, 19.9499999999999) instead of the numbers I should be getting (eg, 19.95)?	[reply]
Re: Pentium math??? by BillKSmith (Friar) on Apr 25, 2012 at 21:10 UTC
It's probably more than you care to know, but all the mathamatical details are expalained at http://www-users.math.umd.edu/~jkolesar/mait613/floating_point_math.pdf	[reply]
Re: Pentium math??? by davido (Bishop) on Apr 25, 2012 at 22:19 UTC
It's shocking, isn't it? Re: shocking imprecision. Dave	[reply]
Re: Pentium math??? by Anonymous Monk on Apr 26, 2012 at 04:30 UTC
See also Is this odd behavior a floating point problem?	[reply]

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