Fixed-precision decimal numbers, where the precision is carried with the numbers at run-time.
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
$3.34.
The number of decimal places in a value is represented as a Word8, allowing for up to 255 decimal places. Functions preserve precision. Addition and subtraction operators return a result with the precision of the most precise argument, so 2.3 + 5.678 = 7.978. Multiplication and division use whatever precision is necessary up to 255 decimal places.
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
or
stack test