string_strip.ml

let string_strip_dir s lst ~right =
  let rec strip s lst' =
    match lst' with 
      [] -> s
    | hd::tail -> 
        let len = String.length s in
        let index = if right then (len - 1) else 0 in
        if (String.get s index) = hd then
          let cropped = if right then String.sub s 0 index else String.sub s 1 (len-1) in
          strip cropped lst
        else
          strip s tail
  in
  strip s lst

let string_lstrip s lst = string_strip_dir s lst ~right:false
let string_rstrip s lst = string_strip_dir s lst ~right:true
let string_strip s lst = string_lstrip (string_rstrip s lst) lst