[Haskell-cafe] Array and Ix for custom Graph ADT

Hi, I'm creating a Graph data structure, and I want to use the array list approach, implemented as an Array. I need my Nodes to be instances of Ix for this to work and my Node type is roughly as follows: data Node = MyNode Int [Int] Type1 Type2 (Type1 and Type2 are nullary algebraic datatypes--enumerations in other words) How can I "index" the Array with an instance of a Node. I think I need to make Node an instance of Ix somehow?? Is this a sensible approach? Sample code of the instance declaration for Ix would be helpful. Thanks Mark Spezzano