How to do round, roundup and rounddown in Perl

[ghung]

Hi Folks,

I am new in Perl and in this forum. I would like to round my decimal number to the nearest integer but I couldn't find such kind of built-in function in perl. Also how about roundup and rounddown? Any comment is highly appreciated.

Many thanks!

Gary

 

[PaulTEG]

from Perl Cookbook (p46,47)

#!/usr/bin/perl
use POSIX;
print "Number\tInt\tFloor\tCeil\tRounded\n";
@array = (3.352, 3.545, 3.725, -3.336);
foreach (@array) {
  printf ( "%.3f\t%.2f\t%.2f\t%.2f\t%.2f\n", $_, int($_), floor($_), ceil($_), sprintf("%.2f",$_));
}

The printf function is just for formatting the output, sprintf rounds up. For more rounding have a look at the math libraries on search.cpan.org.

HTH
--Paul

 

[chazoid]

I think someone mentioned in another thread here a while back that the fastest way to round is to add .5 then use int()

foreach (@array){
$rounded = int($_+.5);
print $rounded,"\n";
}

 

[soy4soy]

int() will always take the integer and drop the fraction.
int(3.9) = 3.0
int(-3.9) = -3.0
int(-3.9+0.5) = -3.0 *this is not proper rounding

ceil() always goes UP:
ceil(3.1) = 3.0
ceil(-3.1) = -3.0

floor() always goes DOWN:
floor(3.9) = 3.0
floor(-3.9) = -4.0

So I propose this logic:

foreach (@array){
if ($_ < 0) {
$rounded = int($_-.5);
} else {
$rounded = int($_+.5);
}
print $rounded,&quot;\n&quot;;
}

 

[soy4soy]

Ooops! Correction:

ceil() always goes UP:
ceil(3.1) = 4.0
ceil(-3.1) = -3.0