readers-v1.adb

task Readers_Writers is
	procedure Reader (Read: out Int);
	entry Writer (Written: in Int);
	entry Begin_Reading;
	entry Finish_Reading;
end;

procedure Reader (Read: out Int) is
begin
	Begin_Reading;
	Read := Shared;
	Finish_Reading;
end;

task body Readers_Writers is
	Shared: Int;
	Readers: Int := 0;
begin
	accept Writer (Written: in Int) do
		Shared := Written;
	end;

	loop
		select
			accept Begin_Reading;
			Readers := Readers + 1;
		or
			accept Finish_Reading;
			Readers := Readers - 1;
		or
			when Readers = 0
				accept Writer (Written: in Int) do
					Shared := Written;
				end;
		end select
	end loop
end Readers_Writers;