Re: [Haskell-cafe] Problem with type in a function

OK. I got it. I was just confused about Double being instance of Ploteable when I have [Double] as an instance. I'm sorry. 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 wrote:

...

Hi,

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?

Thanks!

50 Aniversario de la Cujae. Inaugurada por Fidel el 2 de diciembre de 1964 http://cujae.edu.cu

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-- *Leza Morais Lutonda, Lemol-C* /Electronic and Telecomunicaction Eng./ /Software Development and Architecture Entusiast/ http://lemol.github.io @lemolsoft http://twitter.com/lemolsoft in twitter 50 Aniversario de la Cujae. Inaugurada por Fidel el 2 de diciembre de 1964 http://cujae.edu.cu