deka provides correctly rounded decimal arithmetic for Haskell.
The core of deka is a binding to the C library mpdecimal. You need to install mpdecimal; otherwise, your executables will not link. mpdecimal is available here:
mpdecimal has also been packaged for some Linux distributions, such as Debian (libmpdec-dev) and Arch (mpdecimal). deka has been tested with mpdecimal version 2.4.0.
As the author of deka, I have no association with the author of mpdecimal, and any errors in this library are mine and should be reported to firstname.lastname@example.org or to the Github tracker at
You will want to understand the General Decimal Arithmetic Specification in order to fully understand deka. The specification is at
and more about decimal arithmetic generally at
deka is tested using the tests available on the General Decimal Arithmetic website:
Some of these tests currently fail. The failures are in edge cases that should not affect most usage. Diagnosing these failures is on the TODO list.
Much more documentation is available in the Haddock comments in the source files. There is also a file of examples to get you started. It has copious comments. It is written in literate Haskell, so the compiler keeps me honest with the example code. Unfortunately Haddock does not play very nice with literate Haskell. However, the file is easy to view on Github:
deka is licensed under the BSD license, see the LICENSE file.