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PERL - rounding fractional number

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Top Forums Shell Programming and Scripting PERL - rounding fractional number
# 1  
Old 11-19-2010
Lightbulb PERL - rounding fractional number
It seems that perl sprintf uses the round-to-even method:
PHP Code:
foreach my $i ( 0.5, 1.5, 2.5, 3.5 ) {
    printf "$i -> %.0f\n", $i;
}
__END__

0.5 -> 0
1.5 -> 2
2.5 -> 2
3.5 -> 4
4.5 -> 4 
Where we probably wants to use round-half-up, i.e. output should be as below:

PHP Code:
0.5 -> 1
1.5 -> 2
2.5 -> 3
3.5 -> 4
4.5 -> 5 
Any suggestion to correct the above code to accomplish the above required result?
# 2  
Old 11-19-2010
use the POSIX module and you'll have access to the ceil() and floor() functions.
# 3  
Old 11-19-2010
Hi Pludi,

Thanks a lot for your torch light and solution.

Cheers ~~ / Mysore 101 Ganapati.
# 4  
Old 11-19-2010
The mathematical method is to add 0.5 and then ignore the decimal place.
# 5  
Old 11-19-2010
Question
Another question arises here:

If I use floor(), as:

PHP Code:
#!/usr/bin/perl
use POSIX;
foreach my $i ( 0.4, 0.5, 1.2, 1.6, 2.1, 2.9) {
    printf "$i -> %.0f\n", floor($i);
}
__END__ 
resulting output as:
PHP Code:
0.4 -> 0
0.5 -> 0
1.2 -> 1
1.6 -> 1
2.1 -> 2
2.9 -> 2 

If I use ceil(), as:

PHP Code:
#!/usr/bin/perl
use POSIX;
foreach my $i ( 0.4, 0.5, 1.2, 1.6, 2.1, 2.9) {
    printf "$i -> %.0f\n", ceil($i);
}
__END__ 
resulting:

PHP Code:
0.4 -> 1
0.5 -> 1
1.2 -> 2
1.6 -> 2
2.1 -> 3
2.9 -> 3 

How to roundup the values like,

PHP Code:
if ($any_number >= 0.5) then {
    roundup to its higher number
} else {
    roundup to its lower number
) 
i.e,

result should be as below:

PHP Code:
0.4 -> 0
0.5 -> 1
1.2 -> 1
1.6 -> 2
2.1 -> 2
2.9 -> 3 
Is there any dedicated built-in function in PERL, to accomplish this? Smilie
# 6  
Old 11-19-2010
Short answer: no.

Long answer: See perlfaq4
# 7  
Old 11-19-2010
Install the Perl Math::Round module and use the round() function.

Code:
#!/usr/bin/perl

use Math::Round;

foreach my $i ( 0.4, 0.5, 1.2, 1.6, 2.1, 2.9) {
    printf "$i -> %.0f\n", round($i);
}

This is the output
Code:
0.4 -> 0
0.5 -> 1
1.2 -> 1
1.6 -> 2
2.1 -> 2
2.9 -> 3
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