ShowTrait.fs

module ShowTrait =
    [<Trait>]
    type Show<'T> =
        abstract member show: 'T -> string

    [<Witness>] 
    type ShowInt =
        interface Show<int> with
            member __.show(x) = x.ToString()

    [<Witness>] 
    type ShowFloat =
        interface Show<float> with
            member __.show(x) = x.ToString()
    
    [<Witness>] 
    type ShowSeq<'U, 'T, 'V when 'T :> Show<'U> and 'V :> seq<'U>> =
        interface Show<'V> with
            member __.show(xs) = xs |> Seq.map Show.show |> String.concat "; "

    let show x = Show.show x

open ShowTrait

for i in [1..1000] do
    //sprintf "%A" [1..100]
    sprintf "%s" <| show [1..100]