anchor.diff:    (* ------------------------------------------------------------------------ *)
     (* ------------------------------------------------------------------------ *)
   
  -  let rec concat s = List.fold_left (fun acc x -> cat x acc) empty s
  +  let rec concat s = List.fold (fun acc x -> cat x acc) empty s
     let concat_msb s = concat s
     let concat_lsb s = concat (List.rev s)
   
  
positive.code: 
  /// Functions for converting between numbers in various formats (ints, big ints, strings etc).
  module Conversions = begin
  
    (** Integer to hex character (0..15) *)
    let int_of_hex_char c = 
  
negative.code: 
    (** Converts a decimal number, encoded in a string, to a binary string *)
    let bin_str_of_dec_str width d =
        bin_str_of_big_int width (bigint.Parse d)
  
    (** Converts an array of integers to a binary string *)
    let bin_str_of_int_array l (a:int[]) = 
  