Sprintf.fs

open System.Collections.Generic

type Cache<'T> private () =
    static let d = Dictionary<string,'T>()

    static member Format(format: Printf.StringFormat<'T>) : 'T =
        let key = format.Value
        match d.TryGetValue(key) with
        | true, r -> r
        | _ ->
            let r = sprintf format
            d.Add(key, r)
            r

let sprintf' fmt =
    Cache<_>.Format(fmt)

#time

for i in 1 .. 10000 do
    ignore (sprintf "%i" 15)

for i in 1 .. 10000 do
    ignore (sprintf' "%i" 15)