Removing Descriptors from a String in F #

Question

I am new to functional programming and F #, and there is a lot of information on how to do this (removing certain characters from a string) in F #, but I came across the following function and would like to help a bit to understand exactly what is happening:

let stripchars chars str =
  Seq.fold
    (fun (str: string) chr ->
      str.Replace(chr |> Char.ToUpper |> string, "").Replace(chr |> Char.ToLower |> string, ""))
    str chars

I used the stripchars function by calling it in the split function, which I defined as follows:

let split (str : string) =
    ((stripchars "?,.,!,," str).Split ' ') |> Array.toList

What is hard for me to understand now, in the stripchars function, when the "chars" argument is passed containing a sequence of characters to remove from the str string, it is not even used in the code until the last string "str chars". So how can this work?

Answer 1

, . , , , :

let stripchars chars str =
    let removeOneChar (str : string) chr =
        str.Replace(chr |> Char.ToUpper |> string, "").Replace(chr |> Char.ToLower |> string, "")
    Seq.fold removeOneChar str chars

Seq.fold removeOneChar str chars.

removeOneChar string -> char -> string.