Just bumped into this problem.

Some calculations seem to make a number become a "hidden" real number instead of an integer. The number prints as an integer, but after a substraction with another integer, the result is a real.

#!/usr/bin/perl

use strict; use warnings;

my ($x1, $x2) = (256080, 258160);
my $diff      = $x2 - $x1;

print "x1=$x1, x2=$x2, diff=$diff\n"; # OK

$x2 = 1000*240 + 1000*18 + 1000*( 4/25 ); 
$diff = $x2 - $x1;
print "x1=$x1, x2=$x2, diff=$diff\n"; # Also OK

$x2 = 1000 * ( 4*60 + 18 + 4/25 );
$diff = $x2 - $x1;
print "x1=$x1, x2=$x2, diff=$diff\n"; # $x2 is integer, but $diff is real!

The output is:

x1=256080, x2=258160, diff=2080
x1=256080, x2=258160, diff=2080
x1=256080, x2=258160, diff=2080.00000000003

Or the short one-liner version: perl -e '$x1=256080; $x2 = 1000 * ( 4*60 + 18 + 4/25 ); $diff=$x2-$x1; print "x1=$x1, x2=$x2, diff=$diff, Perl=$^V\n";'

I tried this on Perl versions v5.14.2, v5.18.2 and v5.20.2 with the same result. It is disconcerting that $x2 prints as "258160", but becomes something else when used in a substraction.


In reply to Integers sometimes turn into Reals after substraction by rduke15

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