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@fecrd.cujae.edu.cu> 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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