MODULE Callback EXPORTS Main;

IMPORT IO, Fmt;

TYPE CallBack = PROCEDURE (a: CARDINAL; b: INTEGER);
     Values = REF ARRAY OF INTEGER;

VAR sample := ARRAY [1..5] OF INTEGER {5, 4, 3, 2, 1};
    callback := Display;

PROCEDURE Display(loc: CARDINAL; val: INTEGER) =
  BEGIN
    IO.Put("array[" & Fmt.Int(loc) & "] = " & Fmt.Int(val * val) & "\n");
  END Display;

PROCEDURE Map(VAR values: ARRAY OF INTEGER; size: CARDINAL; worker: CallBack) =
  VAR lvalues := NEW(Values, size);
  BEGIN
    FOR i := FIRST(lvalues^) TO LAST(lvalues^) DO
      worker(i, values[i]);
    END;
  END Map;

BEGIN
  Map(sample, NUMBER(sample), callback);
END Callback.