Take, for example, this function: f :: [Char] -> Char f [] = chr 0 f (c:cs) = chr (ord c + ord (f cs)) [] is typed as [Char], even though it could be typed in infinitely many other ways. Demonstrating yet again, that the compiler *does* use the additional information that it gathers to assist with typing. Regards, John A. De Goes N-BRAIN, Inc. The Evolution of Collaboration http://www.n-brain.net | 877-376-2724 x 101 On Feb 13, 2009, at 6:31 PM, Robert Greayer wrote:
-- John A. De Goes wrote:
Adding information cannot remove a contradiction from the information set available to the compiler.
But it can and often does, for example, for [] or 4. What's the type of either expression without more information?
[] :: [a]
4 :: Num a => a
Do I win something?