Question

#light

let a1 = [| (1, 1); (2, 1); (3, 1) |]

let a2 = [| (1, 1); (2, 3); (3, 1) |]

let aa = Array.zip a1 a2
       |> Array.filter(fun (x, y) -> x <> y)

I want to write a function to do this: it will return the different tuple from two arrays, but I also want to return the index of the different tuple in the second array and the corresponding tuple in the second array. (My code did not work totally yet!)
For my above example, I want to return: 1 and (2, 3)
Another example:

let a1 = [| (1, 1); (2, 1); (3, 1); (4, 1) |]

let a2 = [| (1, 1); (2, 3); (3, 1); (4, 2) |]

I want to return: 1 and (2, 3); 3 and (4, 2)
If you have any idea, please show me your code.
Besides, I am not used to the new place for F#, the format makes me feel difficult to find a good place to post my questions, therefore, I still post my question here.

Answer 1

let a1 = [| (1, 1); (2, 1); (3, 1) |]

let a2 = [| (1, 1); (2, 3); (3, 1) |]

let diff = 
    (a1, a2) 
    ||> Array.mapi2(fun i t1 t2 -> (i, t1, t2))
    |> Array.choose(fun (i, a, b) -> if a <> b then Some (i, b) else None)