And of course it is fun to think about total functions that are "effectively" bottom... id :: a -> a id a = case (a,ack 4 3) of (x,0) -> x

And of course it is fun to think about total functions that are "effectively" bottom... id :: a -> a id a = case (a,ack 4 3) of (x,0) -> x (x,_) -> x where ack 0 n = n+1 ack m 0 = ack (m-1) 1 ack m n = ack (m-1) (ack m (n-1))