The qd package
This package supports both a double-double datatype (approx. 32 decimal digits) and a quad-double datatype (approx. 64 decimal digits), using libqd (which is implemented in C++ with C and Fortran wrappers). To compile this package you need libqd to be installed.
Numeric.QD.DoubleDouble.DoubleDouble and Numeric.QD.QuadDouble.QuadDouble are strict tuples of CDoubles, with the following instances:
But note that the following functions (while present) are undefined:
Non-crashing implementations of these are planned in a future update to this package, as well as instances of Enum and Read.
Additional note: libqd depends on 64bit doubles, while some FPU architectures use 80bit. It is highly recommended to compile with -fno-excess-precision and set the FPU control words to avoid erroneous behaviour, perhaps by doing something like this at the start of your program:
import Foreign (nullPtr) import GHC.Conc (forkOnIO, numCapabilities) import Numeric.QD.FPU.Raw (fpu_fix_start) main :: IO () main = do mapM_ (flip forkOnIO $ fpu_fix_start nullPtr) [ 0 .. numCapabilities - 1 ] -- ...
|Versions||0.1, 0.2, 0.4, 0.4.1, 1.0, 220.127.116.11|
|Upload date||Wed Oct 20 19:54:25 UTC 2010|
|Build failure||ghc-7.0 (log)|