The only possible definition of such a function is something like
unsafeShow :: (forall a . Show a => a) -> String
unsafeShow a = show (a :: Bool)
right?
And you'd also need to coerce the argument type in order to use it:
putStrLn $ unsafeShow $ unsafeCoerce True
Right?
Then a nicer definition might be
unsafeShow :: Show a => a -> b -> String
unsafeShow a b = show (unsafeCoerce b `asTypeOf` a)
Here is an example of how to use it to show an overloaded variable without
changing the type signature:
test :: Eq a => a -> IO ()
test a = putStrLn $ unsafeShow (undefined :: Int) a
Of course, this only works safely if a is an Int:
*Main> test (5 :: Int)
5
*Main> test (5 :: Double)
0
/ Emil
On 2008-01-07 12:56, Lutz Donnerhacke wrote:
* Henning Thielemann wrote:
happen. Paradoxical. It would be interesting if it is possible to tunnel
Show class dictionaries through to an 'error' like IO is tunneled to
'trace'.
unsafeShow :: (forall a . Show a => a) -> String
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