read filename and then open text file

[Bjoern Schiessle <devnull@schiessle.org>]

Hello,
I am an Ada beginner and try do read a filename and then open the file,
but it doesn't work.

I have tried this:

with Ada.Text_IO;
with Ada.Strings.Unbounded;
with Ada.Strings.Unbounded.Text_IO;
use Ada.Text_IO;
use Ada.Strings.Unbounded;
use Ada.Strings.Unbounded.Text_IO;

procedure test is
   file : File_Type;
   filename : Unbounded_String;
begin
   Put_line("Geben Sie das zu erratende Wort ein (nur grossbuchstaben):");
   Put(">");
   Wort := Get_Line;
   Open(Datei, In_File, Dateiname);
   ...

but it doesn't work. I get the message:

expected type "Standard.String"
found private type "Ada.Strings.Unbounded.Unbounded_String"

I have no idea how i must read the filename. Can someone help me?

Thanks a lot
Bjoern