Of course if you want to do it to code independantly of type you need to
redifine show:
data ShowHex = ShowHex
class ShowDict t a where
showDict :: a -> ShowS
instance ShowDict ShowHex Int where
showDict a = showHex a
test :: ShowDict t a => t -> a -> ShowS
test _ a = showDict a
main = putStrLn $ (test ShowHex 27) ""
Keean.
Keean Schupke wrote:
Easy:
data ShowHex a
instance Show (ShowHex a) where
showsPrec _ (ShowHex a) = showHex a
main = putStrLn $ (show (ShowHex 27))
Here, with labelled instances you would write:
show ShowHex 27
instead you write:
show (ShowHex 27)
Keean.
George Russell wrote:
Keean Schupke wrote:
Do you need a language extension at all? You can certainly
do it with the existing extensions!
data ShowDict a
instance Show (ShowDict a) where
showsPrec _ (ShowDict a) = ...
I don't understand. How does that help you to, for example, use a
function which
requires Show Int but (say) substitute the standard function for
which which shows
in hexadecimal?
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