class MAIN is
  -- from, to, step
  for!(once init:INT, once to:INT, once inc:INT):INT is
    i ::= init;
    loop while!( i <= to );
      yield i;
      i := i + inc;
    end;
  end;

  main is
    i, j :INT;
    loop i := for!(1, 5, 1);   -- 1.upto!(5)
      loop j := for!(1, i, 1); -- 1.upto!(i)
        #OUT + "*";
      end;
      #OUT + "\n";
    end;
  end;
end;