[Haskell-cafe] [ANN] deka - decimal arithmetic

Omari Norman omari at smileystation.com
Sat Feb 8 20:06:18 UTC 2014

Announcing deka, a library for decimal arithmetic.

Why decimal arithmetic is important is discussed at length at


but for a short explanation, go into ghci and type:

print $ 0.1 + 0.1 + 0.1

This is 0.3, right? But on my machine I get 0.3 plus a small fraction,
which is simply not acceptable for applications where it is essential to
get exact results, such as financial applications.

deka is a binding to the decNumber C library, a thoroughly tested and fast
implementation of decimal arithmetic.  deka is fully tested and I encourage
you to run the tests using the usual "cabal test" method.

deka is available at


and is on Github at


Because deka is a binding to the decNumber C library, first you will need
to install decNumber.  An easy to install version with the GNU autotools is


decNumber's website is at


A literate Haskell file illustrating the use of deka is available at

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