No subject

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{-# LANGUAGE GADTs #-}
{-# LANGUAGE DeriveDataTypeable #-}

import Data.Typeable

data Box where
    Box :: (Typeable s, Eq s) => s -> Box
    deriving Typeable

instance Eq Box where

    (Box s1) == (Box s2) = Just s1 == cast s2
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that seems to work correctly:
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let a = Box (2::Int)
let b = Box (2::Float)

print $ a == b
print $ a == a
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Is this the right way to go? Is there any other solution?

Thanks,

TP