How can I refer to a specific member of a Tuple of any size in F#

Question

okay, this might be a silly question.

So I have some tuples of size 4 so like (int,int,int,int)

If it were a 2 tuple I could use fst(myTuple) to refer to th

Answer 1

Here's a version of @Daniels novel solution which calculates Rest offsets of the underlying Tuple representation to support position-based access on arbitrarily long tuples. Error handling omitted.

let (@) t idx =
    let numberOfRests = (idx - 1) / 7
    let finalIdx = idx - 7 * numberOfRests
    let finalTuple =
        let rec loop curTuple curRest =
            if curRest = numberOfRests then curTuple
            else loop (curTuple.GetType().GetProperty("Rest").GetValue(curTuple, null)) (curRest+1)
        loop t 0

    finalTuple
     .GetType()
     .GetProperty(sprintf "Item%d" finalIdx)
     .GetValue(finalTuple, null) 
     |> unbox

//fsi usage:
> let i : int = (1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36)@36;;

val i : int = 36