Hi Antoine, The first Int field is a unique index, beginning at 1 and increasing by 1 for each unique Node. The second [Int] field is just a list of random numbers associated with that node. Mark On 14/08/2011, at 2:13 AM, Antoine Latter wrote:

On Sat, Aug 13, 2011 at 4:37 AM, Mark Spezzano wrote:

...

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??

What do the 'Int' and '[Int]' fields represent in your Node type?

Antoine

...

Is this a sensible approach? Sample code of the instance declaration for Ix would be helpful.

Thanks

Mark Spezzano

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Solved it with your help :) Thanks for your assistance! Mark Spezzano On 14/08/2011, at 8:29 AM, Daniel Fischer wrote:

On Sunday 14 August 2011, 00:41:33, Mark Spezzano wrote:

...

Hi Antoine,

The first Int field is a unique index, beginning at 1 and increasing by 1 for each unique Node.

Then you could use that for indexing, assuming the Ord instance matches.

range (MyNode x _ _ _, MyNode y _ _ _) = [x .. y] index (MyNode x _ _ _, MyNode y _ _ _) (MyNode z _ _ _) | x <= z && z <= y = z-x | otherwise = error ("Index out of range: " ++ show z)

etc.

...

The second [Int] field is just a list of random numbers associated with that node.

Mark

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