Question

How can I overload .[] for F# array to slice an array based on an arbitrary index array?

For example:

let x = [|1..10|]; 
let indx = [|4;1|];

although

[| for i in indx ->x.[i]|] 

would work, it would be nicer to be able using x.[indx] directly.

Answer 1

You can always write an F# extension method to get close on the syntax

let a = [| 1..10 |]
let idx = [|4;1|]

type 'T ``[]`` with   //'
    member this.Slice(indices:int array) =
        [| for i in indices -> this.[i] |]

printfn "%A" (a.Slice idx)

but since arrays already have an indexer it doesn’t appear there’s a way to overload/change it.