Alex Watt wrote:
The best way I can explain what I'd like to do is show an example, so here goes:
same :: a -> a -> Bool same x x = True same _ _ = False
Is there any way to do this in Haskell?
No, this is not possible. Each variable bound in a pattern has to be different. Maybe guards are a good alternative: same :: Eq a => a -> a -> Bool same x y | x == y = True same _ _ = False Note that you have to add an Eq constraint.
The actual reason I'd like to do this is something slightly more complicated. I want to match against a list of elements, like so:
foo[x,x,x] = ...
Maybe you can employ the "all" function all :: (a -> Bool) -> [a] -> Bool in a guard, something like foo (x:xs) | all (x ==) xs = ... where you explicitly check that all list elements are equal to the first. Tillmann