type coordinates = ( (Element.t * (float array)) array)

let of_xyz_file ~filename =
  let lexbuf =
    let ic = open_in filename in
    Lexing.from_channel ic
  in
  Xyz_parser.input Nuclei_lexer.read_all lexbuf


let of_zmt_file ~filename =
  let ic = open_in filename in
  let rec aux accu =
    try
      let line = input_line ic in
      aux (line::accu)
    with End_of_file ->
      close_in ic;
      List.rev accu
      |> String.concat "\n"
  in aux []
  |> Zmatrix.of_string
  |> Zmatrix.to_xyz
  |> Array.map (fun (e,x,y,z) -> (e, [|x;y;z|]))