[Haskell-cafe] Define variable types
Martijn van Steenbergen
martijn at van.steenbergen.nl
Thu Feb 5 07:41:39 EST 2009
Hallo Tsunkiet,
Looking at
http://www.cs.uu.nl/wiki/bin/view/Helium/ATourOfTheHeliumPrelude
it seems you're looking for the /. operator, which is division on
floating points. The / you're using only works on integers.
Groetjes,
Martijn.
Tsunkiet Man wrote:
> Hello,
>
> I'm new to Haskell and it seems like a very nice language to learn.
> However I'm not really familiar with the errormessages it produces. I am
> using a Helium interpreter. I've created the following module (however
> it is just a small sketch). I've written the following code:
>
> fac :: Int -> Int
> fac n = product[1..n]
>
> boven :: Int -> Int -> Int
> boven n k = (fac n) `div` fac k * fac (n-k)
>
> bin :: Int -> Int -> Int -> Int
> bin n k p |(n-k)>0 && k>0 = (boven n k) * (p^k) * (1-p)^(n-k)
> |(n-k)<0 && k>0 = (boven n k) * (p^k) * (1/((1-p)^(-(n-k))))
> |(n-k)<0 && k<0 = (boven n k) * (1/(p^(-k))) *
> (1/((1-p)^(-(n-k))))
>
> When I load this into my interpreter it says:
>
> Compiling ./Test.hs
> (11,55): Type error in infix application
> expression : 1 / ((1 - p) ^ (-(n - k)))
> operator : /
> type : Float -> Float -> Float
> does not match : Int -> Int -> Int
> (12,47): Type error in infix application
> expression : 1 / (p ^ (-k))
> operator : /
> type : Float -> Float -> Float
> does not match : Int -> Int -> a
> (12,62): Type error in infix application
> expression : 1 / ((1 - p) ^ (-(n - k)))
> operator : /
> type : Float -> Float -> Float
> does not match : Int -> Int -> a
> Compilation failed with 3 errors
>
> Some details that might be usefull:
>
> Line 11 is |(n-k)<0 && k>0 = (boven n k) * (p^k) * (1/((1-p)^(-(n-k))))
> Line 12 is |(n-k)<0 && k<0 = (boven n k) * (1/(p^(-k))) *
> (1/((1-p)^(-(n-k))))
>
> So my question is: how can I fix these errors?
>
> (I used these lines of codes because it is not possible to use a
> negative exponent in the Helium interpreter.)
>
> Thank you for answering my question!
>
> Greetings JTKM
>
>
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