Andreas.Schroeder@gillardon.de wrote, Generally, did you look at http://haskell.org/ghc/docs/latest/html/users_guide/faster.html
module AIBD(aibd, rechneZins, rechneRate, rechneKapital) where import Foreign(unsafePerformIO)
type Funktion = Double -> Double
data Genauigkeit = Absolut {wert, intervall :: Double} | Intervall Double
See the paragraph under "Use strictness annotations" on the above web page on how to use strictness annotations to speed this data type up.
istOk :: Genauigkeit -> Double -> Double -> Bool istOk (Absolut w i) x _ = abs (x-w) <= i istOk (Intervall i) _ dx = abs dx <= i
sekantenVerfahren :: Funktion -> Genauigkeit -> Genauigkeit -> Int -> Double -> Double sekantenVerfahren f gx gy tiefe start = sekantenIter f tiefe gx gy x1 x2 y1 y2 where x1 = start x2 = start + start * 0.1 y1 = f x1 y2 = f x2 sekantenIter _ 0 _ _ _ x2 _ _ = x2 sekantenIter f tiefe gx gy x1 x2 y1 y2 = let x3 = x2 - y2 * (x2 - x1) / (y2 - y1) y3 = f x3 dy = y3 - y2 dx = x3 - x2 in if (istOk gx x3 dx) && (istOk gy y3 dy) then x3 else sekantenIter f (tiefe-1) gx gy x2 x3 y2 y3
Code like this may benefit from using the option "-O2" and possibly also "-fliberate-case-threshold100" http://haskell.org/ghc/docs/latest/html/users_guide/flag-reference.html#AEN5...
foreign import ccall "HAIBDUtil.h caibd" caibd :: Double -> Double -> Double -> Int -> IO Double
aibd:: Double -> Double -> Double -> Int -> Double aibd kapital zins rate jahre = unsafePerformIO (caibd kapital zins rate jahre) {- does the same than aibd:: Double -> Double -> Double -> Int -> Double aibd kapital _ _ 0 = kapital aibd kapital zins rate jahre = aibd (kapital + kapital * zins - rate) zins rate (jahre-1) -}
Two comments with -O2 -fliberate-case-threshold100 the Haskell version may be as fast as the C version. If not, better foreign import as a pure functions foreign import ccall "HAIBDUtil.h caibd" caibd :: Double -> Double -> Double -> Int -> Double and omit the unsafePerformIO. Cheers, Manuel