MODULE TCoroutine;
// PIM coroutines from SYSTEM: NEWPROCESS / TRANSFER.
// Two coroutines ping-pong; after 5 transfers Pong hands control
// back to the main process, which checks the counter and exits 42.
FROM SYSTEM IMPORT ADDRESS, PROCESS, NEWPROCESS, TRANSFER, ADR;

CONST Stack = 65536;

VAR ping, pong, exits : PROCESS;
VAR ws1, ws2 : ARRAY [0..65535] OF CHAR;
VAR count : CARDINAL;
VAR ExitCode : INTEGER;

PROCEDURE Ping;
BEGIN
  LOOP
    TRANSFER(ping, pong)
  END
END Ping;

PROCEDURE Pong;
BEGIN
  LOOP
    INC(count);
    IF count >= 5 THEN TRANSFER(pong, exits) END;
    TRANSFER(pong, ping)
  END
END Pong;

BEGIN
  NEWPROCESS(Ping, ADR(ws1), Stack, ping);
  NEWPROCESS(Pong, ADR(ws2), Stack, pong);
  TRANSFER(exits, ping);
  IF count = 5 THEN ExitCode := 42 ELSE ExitCode := 1 END
END TCoroutine.