I'm really inexperienced at this :
-----------
{-# OPTIONS_GHC -fglasgow-exts -funbox-strict-fields
-fallow-undecidable-instances -O2 #-}
class Gadget g where
fInit :: g -> a -> g
data FString = FString !Int !String deriving Show
instance Gadget FString where
fInit (FString n _) s = FString n (take n s)
-------------
I get the error message :
Couldn't match expected type `String' against inferred type `a'
`a' is a rigid type variable bound by
the type signature for `fInit' at Gadget.hs:4:17
In the second argument of `FString', namely `s'
In the expression: FString n s
In the definition of `fInit': fInit (FString n _) s = FString n s
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