F# function to join sequence of strings using a delimiter without conversion to array

gistfile1.fs

open System
open System.Text

/// Join a sequence of strings using a delimiter.
/// Equivalent to String.Join() but without arrays.
let join (items : seq<string>) (delim : string) =
    // Collect the result in the string builder buffer
    // The end-sequence will be "item1,delim,...itemN,delim"
    let buff = 
        Seq.fold 
            (fun (buff :StringBuilder) (s:string) -> buff.Append(s).Append(delim)) 
            (new StringBuilder()) 
            items

    // We don't want the last delim in the result buffer, remove
    buff.Remove(buff.Length-delim.Length, delim.Length).ToString()

Hi thanks for this example!!
I have created a modified version based on your example

/// Join a sequence of strings using a delimiter.
let join (delim : string) (items : seq<'items>) =
    System.String.Join(delim, items)


// Example calls
// Join string array by spaces
printfn "%s" (join " " ["This"; "is"; "some"; "text"])

// Join int list on "-" and call from a pipeline
[1..10]
|> join "-"
|> printfn "%s"