error.txt

[1 of 1] Compiling Main             ( test.hs, test.o )

test.hs:8:36:
    No instance for (Num (a0 -> Double)) arising from a use of `y'
    Possible fix: add an instance declaration for (Num (a0 -> Double))
    In the first argument of `(*)', namely `(y x)'
    In the expression: (y x) * 0.001
    In the first argument of `sum', namely
      `[(y x) * 0.001 |
          x <- [(fromIntegral l) + 0.0005, (fromIntegral l)
                                           + 0.0015 .. (fromIntegral r)]]'

test.hs:8:55:
    No instance for (Enum a0)
      arising from the arithmetic sequence `(fromIntegral l)
                                            + 0.0005, (fromIntegral l) + 0.0015 .. (fromIntegral r)'
    The type variable `a0' is ambiguous
    Possible fix: add a type signature that fixes these type variable(s)
    Note: there are several potential instances:
      instance Enum Double -- Defined in `GHC.Float'
      instance Enum Float -- Defined in `GHC.Float'
      instance Integral a => Enum (GHC.Real.Ratio a)
        -- Defined in `GHC.Real'
      ...plus 7 others
    In the expression:
      [(fromIntegral l) + 0.0005, (fromIntegral l)
                                  + 0.0015 .. (fromIntegral r)]
    In a stmt of a list comprehension:
      x <- [(fromIntegral l) + 0.0005, (fromIntegral l)
                                       + 0.0015 .. (fromIntegral r)]
    In the first argument of `sum', namely
      `[(y x) * 0.001 |
          x <- [(fromIntegral l) + 0.0005, (fromIntegral l)
                                           + 0.0015 .. (fromIntegral r)]]'

test.hs:8:72:
    No instance for (Num a0) arising from a use of `+'
    The type variable `a0' is ambiguous
    Possible fix: add a type signature that fixes these type variable(s)
    Note: there are several potential instances:
      instance Num Double -- Defined in `GHC.Float'
      instance Num Float -- Defined in `GHC.Float'
      instance Integral a => Num (GHC.Real.Ratio a)
        -- Defined in `GHC.Real'
      ...plus three others
    In the expression: (fromIntegral l) + 0.0005
    In the expression:
      [(fromIntegral l) + 0.0005, (fromIntegral l)
                                  + 0.0015 .. (fromIntegral r)]
    In a stmt of a list comprehension:
      x <- [(fromIntegral l) + 0.0005, (fromIntegral l)
                                       + 0.0015 .. (fromIntegral r)]

test.hs:8:73:
    No instance for (Fractional a0) arising from the literal `0.0005'
    The type variable `a0' is ambiguous
    Possible fix: add a type signature that fixes these type variable(s)
    Note: there are several potential instances:
      instance Fractional Double -- Defined in `GHC.Float'
      instance Fractional Float -- Defined in `GHC.Float'
      instance Integral a => Fractional (GHC.Real.Ratio a)
        -- Defined in `GHC.Real'
    In the second argument of `(+)', namely `0.0005'
    In the expression: (fromIntegral l) + 0.0005
    In the expression:
      [(fromIntegral l) + 0.0005, (fromIntegral l)
                                  + 0.0015 .. (fromIntegral r)]

some.hs

import Text.Printf (printf)

-- This function should return a list [area, volume].
solve :: Int -> Int -> [Int] -> [Int] -> [Double]
solve l r as bs = [area]
                  where
                      y x = sum $ zipWith (\a b -> (fromIntegral a)(x*(fromIntegral b))) as bs
                      area = sum [(y x) * 0.001 | x <-[(fromIntegral l)+0.0005, (fromIntegral l)+0.0015..(fromIntegral r)]]

--Input/Output.
main :: IO ()
main = undefined
--main = getContents >>= mapM_ (printf "%.1f\n"). (\[a, b, [l, r]] -> solve l r a b). map (map read. words). lines