How do you calculate div and mod of floating point numbers?
- by boost
In Perl, the % operator seems to assume integers. For instance:
sub foo {
my $n1 = shift;
my $n2 = shift;
print "perl's mod=" . $n1 % $n2, "\n";
my $res = $n1 / $n2;
my $t = int($res);
print "my div=$t", "\n";
$res = $res - $t;
$res = $res * $n2;
print "my mod=" . $res . "\n\n";
}
foo( 3044.952963, 7.1 );
foo( 3044.952963, -7.1 );
foo( -3044.952963, 7.1 );
foo( -3044.952963, -7.1 );
gives
perl's mod=6
my div=428
my mod=6.15296300000033
perl's mod=-1
my div=-428
my mod=6.15296300000033
perl's mod=1
my div=-428
my mod=-6.15296300000033
perl's mod=-6
my div=428
my mod=-6.15296300000033
Now as you can see, I've come up with a "solution" already for calculating div and mod. However, what I don't understand is what effect the sign of each argument should have on the result. Wouldn't the div always be positive, being the number of times n2 fits into n1? How's the arithmetic supposed to work in this situation?
