ADA and Open GL

["ldries46" <bertus.dries@planet.nl>]

I do have a program where I have to create an OpenGL window in a selected 
number of cases.
The routine in which that happens is:

procedure InitGlutWindow( argc : integer; argv : string; Xpos : integer; 
Ypos : integer; Width : integer; Height : integer;  WindowName : string ) is
   argca : aliased integer := argc;
   winna : aliased string := WindowName;
   pargv : Interfaces.C.Strings.chars_ptr;
   pwin  : GLubytePtr := Interfaces.C.Strings.New_String(WindowName);
begin
   pargv := Interfaces.C.Strings.New_String(argv);
   glutInit( argca'Access, pargv );
   glutInitDisplayMode (GLUT_DOUBLE);
   glLoadIdentity;
   gluLookAt(eyex, eyey, eyez, refx, refy, refz, dirx, diry, dirz);
   glutInitWindowSize( Width, Height );
   glutInitWindowPosition( Xpos, Ypos );
   glutCreateWindow( pwin );                   -- Create the Window PROBLEM
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity;
   glOrtho( -0.5*vOrtho, vOrtho, -0.5*vOrtho, 0.5*vOrtho, -0.5*vOrtho, 
0.5*vOrtho );
   glMatrixMode(GL_MODELVIEW);
end InitGlutWindow;

When compiling I get the error message:

cannot use function "glutCreateWindow" in a procedure call

when I create a function in stead of a procedure I get the same error 
message

What can I do to make this work.

L. Dries