And I can declare an instance for (x, y) which does NOT implies (Show x):
instance Show (x, y) where
show _ = "I'm tuple! Hooray!"
Andrew Coppin
Cannot deduce (Show x) from context (Show (x, y)). Cannot deduce (Show y) from context (Show (x, y)).
Um... seriously?
From Prelude, we have
Show x, Show y => Show (x, y)
So clearly it works in the forward direction. But apparently not in the reverse direction.
Is this a bug or a feature? (I.e., is there some obscure possibility I haven't thought of which means that doing the reverse inference would be incorrect?)
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe