CODEWITHSUNDEEP
listhaskell
user4406515
user4406515

Reputation:

How to fix parse error (possibly incorrect indentation or mismatched brackets) in Haskell

I wrote the following code and put the error in the title. Can someone help me please? Error in line 7

punkteImKreis :: Double -> [(Double, Double)]
punkteImKreis k = [(x,y)|x <- [1.0,2.0..k-1.0],
                         y <- [1.0,2.0..k-1.0] ]

anteilImKreis :: Double -> Double
let l = length(punkteImKreis)
in anteilImKreis k = (fromIntegral (l)) / k^2

Upvotes: 1

Views: 247

Answers (1)

bradrn
bradrn

Reputation: 8477

The error is in this definition:

anteilImKreis :: Double -> Double
let l = length(punkteImKreis)
in anteilImKreis k = (fromIntegral (l)) / k^2

let is an expression; therefore, it has to be inside a definition (that is, on the right of an = sign). This should be:

anteilImKreis :: Double -> Double
anteilImKreis k =
  let l = length(punkteImKreis)
  in (fromIntegral (l)) / k^2

By the way, you don't really need parentheses around an argument of a function when it's just one identifier. I would rewrite this as follows:

anteilImKreis :: Double -> Double
anteilImKreis k =
  let l = length punkteImKreis
  in (fromIntegral l) / k^2

Additionally, this exposes another error. punkteImKreis isn't a list; it's a function which returns a list, which means you can't directly take its length. I would assume you meant the following:

anteilImKreis :: Double -> Double
anteilImKreis k =
  let l = length (punkteImKreis k)
  in (fromIntegral l) / k^2

Upvotes: 5

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