MODULE procpointer;

FROM Printf IMPORT printf;

TYPE
    Callable = PROCEDURE(INTEGER): INTEGER;

PROCEDURE inc(x: INTEGER): INTEGER;
BEGIN
    RETURN x + 1;
END inc;

PROCEDURE dec(x: INTEGER): INTEGER;
BEGIN
    RETURN x - 1;
END dec;

PROCEDURE runner(VAR x: INTEGER; func: Callable);
BEGIN
    x := func(x);
END runner;

VAR x: INTEGER;

BEGIN
   x := 0;
   printf("%d\n", x);

   runner(x, inc);
   printf("%d\n", x);

   runner(x, dec);
   printf("%d\n", x);


END procpointer.