let getSubsets list =
    let rec generateSubsets list acc compacc =
        seq {
            match list with
            | [] -> yield acc
            | head::tail ->
                yield! generateSubsets tail (head::acc) compacc
                yield! generateSubsets tail acc (head::compacc)
        }

    (generateSubsets list [] []) |> Seq.toArray

let getResults list =
    let getCalcString calcstr op head =
        if calcstr = "" then
            head
        else
            calcstr + " " + op + " " + head

    let rec loop list result calcstr =
        seq {
            match list with
            | [] -> yield (result, calcstr)
            | head::tail ->
                let headstr = head.ToString()
                yield! loop tail (result + head) (getCalcString calcstr "+" headstr)
                yield! loop tail (result - head) (getCalcString calcstr "-" headstr)
                yield! loop tail (head - result) (getCalcString headstr "-" calcstr)
                yield! loop tail (result * head) (getCalcString calcstr "*" headstr)
                if head <> 0 then
                    yield! loop tail (result / head) (getCalcString calcstr "/" headstr)
                if result <> 0 then
                    yield! loop tail (head / result) (getCalcString headstr "/" calcstr)
        }

    let run list =
        match list with
        | [] -> Seq.empty
        | head::tail -> loop tail head (head.ToString())

    run list

// only works for sets with 3 numbers or larger
let calculate subsets =
    if subsets |> Array.length < 8 then
        ()
    else
        for i in 1..subsets.Length/2 do
            (getResults subsets.[i])
            |> Seq.iter(fun (result, calcstr) ->
                (getResults subsets.[subsets.Length-1-i])
                |> Seq.iter(fun (result2, calcstr2) ->
                    if result = result2 then
                        printfn "%s = %s "calcstr calcstr2))


calculate (getSubsets [1;2;3;6])