Runge-Kutta method: Difference between revisions
→{{header|Haskell}}: Minor tidying of existing draft - removed redundant import, applied hlint, hindent.
(→{{header|Haskell}}: Minor tidying of existing draft - removed redundant import, applied hlint, hindent.) |
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Line 825:
Using GHC 7.4.1.
<lang haskell>
:: Floating a
=> a -> a -> a
dv = (. sqrt) . (*)▼
▲dv = (. sqrt). (*)
rk4
:: (Enum a, Fractional a)
where
ts = [a,h ..]▼
fc t y =
scanl
(h * fd t y)
[1 / 2, 1 / 2, 1]
task =
▲rk4 :: (Enum a, Fractional a)=> (a -> a -> a) -> a -> a -> a -> [(a,a)]
mapM_
▲rk4 fd y0 a h = zip ts $ scanl (flip fc) y0 ts where
▲ ts = [a,h ..]
▲ fc t y = sum. (y:). zipWith (*) [1/6,1/3,1/3,1/6]
▲ $ scanl (\k f -> h * fd (t+f*h) (y+f*k)) (h * fd t y) [1/2,1/2,1]
▲ $ map (\(x,y)-> (truncate x,y,fy x - y))
▲ $ filter (\(x,_) -> 0== mod (truncate $ 10*x) 10)
▲ $ take 101 $ rk4 dv 1.0 0 0.1</lang>
Example executed in GHCi:
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