BSD3 licensed by Paul Johnson
Maintained by

Module documentation for 0.4.2

Variable Precision Decimal Numbers

The "Decimal" type is mainly intended for doing financial arithmetic
where the number of decimal places may not be known at compile time
(e.g. for a program that handles both Yen and Dollars) and the
application must not drop pennies on the floor. For instance if you
have to divide $10 between three people then one of them has to get

The number of decimal places in a value is represented as a Word8,
allowing for up to 255 decimal places. Functions preserve precision.
Binary operators return a result with the precision of the most
precise argument, so 2.3 + 5.678 = 7.978.

If you need fixed precision decimal arithmetic where the precision is
known at compile time then Data.Number.Fixed from Lennart Augustsson's
"numbers" package is more likely to be what you want.

QuickCheck Specification

Data.Decimal includes a set of QuickCheck properties which act as both
tests and a formal specification. To run the tests do:

cabal configure --enable-tests
cabal build
cabal test

Version 0.2.1

Fixed "base" dependency.
Put test suite under "cabal test"

Version 0.2.2

Minor fixes to allow compilation under other versions of GHC.

Version 0.2.3

Added instance of NFData from Control.DeepSeq, and hence a dependency
on the deepseq package, thanks to Jeff Shaw (shawjef3 at

Version 0.3.1

Added Typeable, Fractional and RealFrac instances.
Multiplication now returns an exact result, increasing precision if necessary.

These changes alter the API. Hence the increment to the major version number.

Thanks to Alexey Uimanov (s9gf4ult at

Version 0.4.1

Improved "Read" instance. Now handles "1.2e3" and "reads" only returns a
single parse.
Corrected documentation.
Added "Enum" instance.
"decimalConvert" now returns a Maybe value. The old version has been renamed
to "unsafeDecimalConvert.

Version 0.4.2

Removed spurious "Integer" type context.

comments powered byDisqus