Math::FixedPrecision - Decimal Math without Floating Point Errors |
Math::FixedPrecision - Decimal Math without Floating Point Errors
use Math::FixedPrecision; $height = Math::FixedPrecision->new(12.362); # 3 decimal places $width = Math::FixedPrecision->new(9.65); # 2 decimal places $area = $height * $width; # area is now 119.29 not 119.2933 $length = Math::FixedPrecision->new(``100.00''); # 2 decimal places $section = $length / 9; # section is now 11.11 not 11.1111111...
There are numerous instances where floating point math is unsuitable, yet the
data does not consist solely of integers. This module employs new features
in Math::BigFloat to automatically maintain precision during math operations.
This is a convenience module, since all of the operations are handled by
Math::BigFloat internally. You could do everything this module does by
setting some attributes in Math::BigFloat. This module simplifies that
task by assuming that if you specify a given number of decimal places in
the call to new()
then that should be the precision for that object going
forward.
Please examine assumptions you are operating under before deciding between this module and Math::BigFloat. With this module the assumption is that your data is not very accurate and you do not want to overstate any resulting values; Math::BigFloat can unintentially inflate the apparent accuracy of a calculation.
new(number[,precision])
The constructor accepts either a number or a string that looks like a number. But if you want to enforce a specific precision, you either need to pass an exact string or include the second term. In other words, all of the following variables have different precisions:
$var1 = Math::FixedPrecision->new(10); # 10 to infinite decimals $var2 = Math::FixedPrecision->new(10,2); # 10.00 to 2 decimals $var3 = Math::FixedPrecision->new("10.000"); # 10.000 to 3 decimals
All calculations will return a value rounded to the level of precision of the least precise datum. A number which looks like an integer (like $var1 above) has infinite precision (no decimal places). This is important to note since Perl will happily truncate all trailing zeros from a number like 10.000 and the code will get 10 no matter how many zeros you typed. If you need to assert a specific precision, you need to either explicitly state that like $var2 above, or quote the number like $var3. For example:
$var4 = $var3 * 2; # 20.000 to 3 decimals $var5 = Math::FixedPrecision->new("2.00"); # 2.00 to 2 decimals $var6 = $var3 * $var 5; # 20.00 to 2 decimals, not 3
=head2 EXPORT None by default.
=head1 AUTHOR
John Peacock <jpeacock@rowman.com>
Math::BigFloat
Math::FixedPrecision - Decimal Math without Floating Point Errors |