in reply to decimal precision

There are many ways to solve the problem, but here's a trick that may not leap straight to your finger tips:

use warnings;
use strict;
use bignum;

my $e = 0.00141;
my $o =1;
for (1 .. 10){
    "@{[$o *= $e]}" =~ /(0\.0*\d{0,5})/;
    print "$1\n";
}

[download]

Prints:

0.00141
0.0000019881
0.0000000028032
0.0000000000039525
0.0000000000000055730
0.0000000000000000078580
0.000000000000000000011079
0.000000000000000000000015622
0.000000000000000000000000022027
0.000000000000000000000000000031059

[download]

The @{[...]} trick is useful for interpolating the result of a chunk of code into a string. The rest should be pretty obvious, but note that if the regex doesn't match the print may generate some interesting results.

Update: bah, forgot about the rounding. Oh well, the interpolation trick is still worth knowing even if it doesn't really help solve the OP's problem.

Perl is environmentally friendly - it saves trees

Replies are listed 'Best First'.
Re^2: decimal precision
by almut (Canon) on May 30, 2008 at 11:44 UTC
    The @{[...]} trick is useful for interpolating the result of a chunk of code into a string.

    No doubt a nice trick... but in this particular case, the conversion to string would happen implicitly, i.e. you could also do 

        ($o *= $e) =~ /(0\.0*\d{0,5})/;

    [download]

    Yet another way would be to use bignum's accuracy option (which also does take care of the rounding) 

    use bignum accuracy => 5;

my $e = 0.00141;
my $o = 1;
for (1 .. 10) {
    $o *= $e;
    print "$o\n";
}
__END__
0.0014100
0.0000019881
0.0000000028032
0.0000000000039525
0.0000000000000055730
0.0000000000000000078579
0.000000000000000000011080
0.000000000000000000000015623
0.000000000000000000000000022028
0.000000000000000000000000000031059

    [download]

    (see Math::BigInt and Math::BigFloat for details on rounding modes, accuracy, precision, etc.)

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