[Haskell-cafe] Problem with type in a function
Leza Morais Lutonda
leza.ml at fecrd.cujae.edu.cu
Wed Jul 2 20:13:51 UTC 2014
OK. I got it.
I was just confused about Double being instance of Ploteable when I have
[Double] as an instance.
On 02/07/14 16:07, MigMit wrote:
> Exactly what it is telling you you're missing. You said "plotf applies to any type 'a' if it's of class Ploteable". Then you try to use it with a=Double. So, it doesn't see how Double is of class Ploteable.
> On 02 Jul 2014, at 23:52, Leza Morais Lutonda <leza.ml at fecrd.cujae.edu.cu> wrote:
>> I have the following function
>> plotf :: Ploteable a => ([a] -> IO ()) -> (a -> a) -> [a] -> IO ()
>> plotf plot fn xs = plot $ map fn xs
>> that compiles correctly, but when I use it with:
>> plotf win sin [1..100::Double] -- where win :: [Double] -> IO ()
>> I'm geting the error:
>> No instance for (Ploteable Double) arising from a use of ‘plotf’
>> In the expression: plotf win sin [1 .. 100 :: Double]
>> In an equation for ‘it’: it = plotf win sin [1 .. 100 :: Double]
>> What am I missing?
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*Leza Morais Lutonda, Lemol-C*
/Electronic and Telecomunicaction Eng./
/Software Development and Architecture Entusiast/
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50 Aniversario de la Cujae. Inaugurada por Fidel el 2 de diciembre de 1964 http://cujae.edu.cu
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