let escape s =
  let b = Buffer.create (String.length s + 8) in
  String.iter
    (fun c ->
      match c with
      | '"' -> Buffer.add_string b "\\\""
      | '\\' -> Buffer.add_string b "\\\\"
      | '\n' -> Buffer.add_string b "\\n"
      | '\t' -> Buffer.add_string b "\\t"
      | '\r' -> Buffer.add_string b "\\r"
      | c when Char.code c < 0x20 -> Buffer.add_string b (Printf.sprintf "\\u%04x" (Char.code c))
      | c -> Buffer.add_char b c)
    s;
  Buffer.contents b

let str s = "\"" ^ escape s ^ "\""
let list f l = "[" ^ String.concat ", " (List.map f l) ^ "]"