-- Code of Figure 14.11, page 659 from
-- Kenneth C. Louden, Programming Languages
-- Principles and Practice 2nd Edition
-- Copyright (C) Brooks-Cole/ITP, 2003
-- A Semaphore as a task type in Ada83

task type Semaphore is
  entry initSem (n: in integer);
  entry wait;
  entry signal;
end;

task body Semaphore is
  count : integer;
begin
  accept initSem (n: in integer) do
    count := n;
  end;
  loop
    select
      when count > 0 =>
        accept wait;
        count := count - 1 ;
    or
      accept signal;
      count := count + 1;
    or
      terminate;
    end select;
  end loop;
end Semaphore;