[Haskell-cafe] Having trouble with instance context
Kurt Stutsman
kstutsman at gmail.com
Wed Feb 23 03:10:58 CET 2011
I am trying to create an instance of a class for data types deriving
from Enum. When I try to specify this through a context on the instance
definition, I get an error. When I do something similar with a function,
it seems to work fine. Why does the instance not work?
{------------ Example: ---------------}
class Test t where
func :: t -> Int
-- This instance does not compile
instance (Enum e) => Test e where
func x = fromEnum x
-- This function does work
newfunc :: (Enum e) => e -> Int
newfunc x = fromEnum x
Thanks,
Kurt
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