Strip a set of characters from a string

Strip a set of characters from a string is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

The task is to create a function that strips a set of characters from a string. The function should take two arguments: the first argument being a string to stripped and the second, a string containing the set of characters to be stripped. The returned string should contain the first string, stripped of any characters in the second argument:

<lang pseudocode> print stripchars("She was a soul stripper. She took my heart!","aei")
Sh ws  soul strppr. Sh took my hrt!</lang>

OCaml

<lang ocaml>let stripchars s cs =

 let len = String.length s in
 let res = String.create len in
 let rec aux i j =
   if i >= len then String.sub res 0 j
   else match String.contains cs s.[i] with
   | true ->
       aux (succ i) (j)
   | false ->
       res.[j] <- s.[i];
       aux (succ i) (succ j)
 in
 aux 0 0</lang>

testing in the toplevel:

# stripchars "She was a soul stripper. She took my heart!" "aei" ;;
- : string = "Sh ws  soul strppr. Sh took my hrt!"