[Haskell-cafe] Query regarding Type classes
arun.suresh at gmail.com
Mon Oct 13 05:33:02 EDT 2008
Im kinda new to haskell. Ive only been fiddling around with it for bout 3 -
4 weeks now.
And for the life of me... i cant seem to figure out why this doesnt work :
class Foo a where
fooFunc :: a -> Int
data FooData = FData
instance Foo FooData where
fooFunc _ = 10
class Bar a where
barFunc :: (Foo b) => a -> b -> Int
data BarData = BData
instance Bar BarData where
barFunc _ FData = 20
When I compile I get this :
Couldn't match expected type `b' against inferred type `FooData'
`b' is a rigid type variable bound by
the type signature for `barFunc' at Sample.hs:16:20
In the pattern: FData
In the definition of `barFunc': barFunc _ FData = 20
In the definition for method `barFunc'
Think Im missing something really big...
Could somebody kindly help me out here...
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