in reply to Fixed precision numbers

You can use sprintf('%.2f', $foo) to round it. There's probably a module does this automatically, but creating one isn't hard. Just tie a variable. 

{
    package BlahBlah;
    use Tie::Scalar;
    @ISA = 'Tie::StdScalar';
    sub STORE { ${+shift} = sprintf '%0.2f', pop }
}

tie my $foo, 'BlahBlah'; 

$foo = 1;
print "$foo\n";  # 1.00

$foo = 1.005;
print "$foo\n";  # 1.00

$foo = 1.025;
print "$foo\n";  # 1.02

$foo = 0;
print "$foo\n";  # 0.00

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Juerd
- http://juerd.nl/
- spamcollector_perlmonks@juerd.nl (do not use).

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Re: Re: Fixed precision numbers
by dash2 (Hermit) on Feb 25, 2003 at 22:10 UTC
    It's not that simple. sprintf rounds mathematically (rounding .5 up or down, depending on... I think whether the integer portion is odd or even).

    for (0.35,0.45){print sprintf("%.1f",$_);print "\n"}
# result:
0.3 
0.5

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    That won't work for accounting: you always need to round up.

    Dave

[reply]
[d/l]

      That won't work for accounting: you always need to round up.

      No, it won't work for maths, but it *will* work for accounting. I think it was merlyn who told me sprintf's rounding was called "Banker's rounding" and showed me why it was important. Google has a lot of information about this phenomenon. In short: halves are rounded towards the nearest even integer, and that solves a lot of problems.

      I don't know about international accounting differences, but I don't think biasing rounding up is a good thing to do. 

      Juerd
- http://juerd.nl/
- spamcollector_perlmonks@juerd.nl (do not use).

[reply]
        Sounds like we need someone with accounting knowledge to deliver wisdom.... Interesting, anyway.

        dave hj~

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