Re: [Haskell-beginners] Question about List Type Constraint and Null

El sáb, 22-01-2011 a las 00:03 -0600, aditya siram escribió:

But I have a further question why should 'null ...' care about the type of its list argument? Isn't it polymorphic? So it shouldn't make a difference that the 'a' inside res is ambiguous because we know for sure that it always returns a list of some kind.

The point is that for different types for res, the list has a different number of elements. So without saying what the type of res is, you cannot know if the list is empty or not. Jürgen