Question

a simple example of what I would like to do is

 Array.tryFind (fun elem index -> elem + index = 42) array1  //not valid

Since there is no break or continue, i find it hard to do it manually even in a for loop

Answer 1

Similar with @gradbot’s answer, you could define a module function along the line of mapi, iteri which works on arrays, lists and sequences.

module Seq =
    let tryFindi fn seq =
        seq |> Seq.mapi (fun i x -> i, x)
            |> Seq.tryFind (fun (i, x) -> fn i x)
            |> Option.map snd

// Usage
let res = [|1;1;40;4;2|] |> Seq.tryFindi (fun i el -> i + el = 42)