gnat: time-slicing

[Jan Prazak <janp9@gmx.net>]

Hello,

I have seen this example program in a tutorial:

------------
with Ada.Text_IO; use Ada.Text_IO;

procedure Task_Demo is
  task A;
  task body A is
  begin
    Put_Line("b");
    Put_Line("b");
  end A;
begin
  Put_Line("a");
  Put_Line("a");
end Task_Demo;
---------------

The output is:
a
a
b
b

But I want the output to be:

ab

ab

(the tutorial says that this is the output with enabled time-slicing)

I have tried to use -gnatT100, and -gnatT1, and pragma
Time_Slice(0.000001) etc., but none of this works.
I have gnat for Linux.

Jan