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surganov/1-29.hs

Created August 23, 2014 19:26
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1-29.hs
cube :: Float -> Float
cube x = x * x * x
sum' :: (Float -> Float) -> Float -> (Float -> Float) -> Float -> Float
sum' term a next b =
if a > b
then 0
else term a + sum' term (next a) next b
integral :: (Float -> Float) -> Float -> Float -> Float -> Float
integral f a b n = (h / 3) * (sum' term 0 (+1) n) where
h = (b - a) / n
y k = f $ a + k * h
term k
| k == 0 || k == n = y k
| odd k = 4 * y k
| even k = 2 * y k
main = do
print $ integral cube 0 1 100
-- No instance for (Integral Float) arising from a use of `odd'
-- Possible fix: add an instance declaration for (Integral Float)
-- In the expression: odd k
-- In a stmt of a pattern guard for
-- an equation for `term':
-- odd k
-- In an equation for `term':
-- term k
-- | k == 0 || k == n = y k
-- | odd k = 4 * y k
-- | even k = 2 * y k
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