On Fri, 17 Nov 2006 18:36:30 +0100, you wrote:
But I need something which is heterogeneous and non-fixed length. I'm used do Java, and this switch to functional languages is very strange to me. So, to be clear, I need something like LinkedList<Object> in java.
In an attempt to leverage your existing Java knowledge... In Java, while the "things" in your list are heterogeneous at some level, they are homogeneous at another: They are all instances of Object (or a subclass thereof). You can't, for example, put an int in your list. And in fact, that's a primary reason for the existence of the Integer class--it makes your int look like an Object, so that you can treat it like one. (And similarly for Character, Float, Double, etc.) So you do the analogous thing in Haskell: First, you ask yourself, "What kinds of things do I want to put in my list?" Once you have the answer to that, you ask, "Are these things homogeneous at some level?" If they are, then you make your list a list of those homogenous things (actually, the compiler generally does it for you). If they aren't, then you wrap them up in a homogeneous wrapper in exactly the same way as you wrap your int in an Integer, your double in a Double, etc., in Java. Some of the other replies have shown you how to declare this; it's trivially simple: data MyHomogeneousWrapper = Integer Int | Character Char | Float Float deriving Show Finally, constructing new instances of this homogenous wrapper in Haskesll is just like it is in Java: myList = [(Integer 42), (Character 'a'), (Float 3.14159)] vs. myList = new LinkedList(); myList.add(new Integer(42)); myList.add(new Character('a')); myList.add(new Float(3.14159)); Steve Schafer Fenestra Technologies Corp. http://www.fenestra.com/