StringBuffer.fs

[<AutoOpen>]
module StringBuffer =
    open System.Text

    type StringBuffer = StringBuilder -> unit

    type StringBufferBuilder () =
        member inline _.Yield (txt: string) = fun (b: StringBuilder) -> b.Append txt |> ignore
        member inline _.Yield (c: char) = fun (b: StringBuilder) -> b.Append c |> ignore
        member inline _.Yield (strings: #seq<string>) =
            fun (b: StringBuilder) -> for s in strings do s |> b.AppendLine |> ignore
        member inline _.YieldFrom (f: StringBuffer) = f
        member inline _.Combine (f, g) = fun (b: StringBuilder) -> f b; g b
        member inline _.Delay f = fun (b: StringBuilder) -> (f()) b
        member inline _.Zero () = ignore
        
        member inline _.For (xs: 'a seq, f: 'a -> StringBuffer) =
            fun (b: StringBuilder) ->
                let e = xs.GetEnumerator ()
                while e.MoveNext() do
                    (f e.Current) b
        
        member inline _.While (p: unit -> bool, f: StringBuffer) =
            fun (b: StringBuilder) -> while p () do f b
            
        member inline _.Run (f: StringBuffer) =
            let b = StringBuilder()
            do f b
            b.ToString()

    let stringBuffer = new StringBufferBuilder ()

let _ = stringBuffer {
    yield sprintf "%d" 1 // тут ок
}

let _ = stringBuffer {
    sprintf "%d" 1 // тут нет хинта и экшена
}