一般的な可変長引数関数

  Func void foo()
  {
    Matrix a, b, c;
    Matrix afo(...);

    read a, b, c;

    print afo();
    print afo(a);
    print afo(a, b);
    print afo(a, b, c);
  }

  Func Matrix afo(a, b, c, ...)
    Matrix a, b, c;
  {
    if (nargs == 0) {
      return Z(0);
    } else if (nargs == 1) {
      return a;
    } else if (nargs == 2) {
      return a + b;
    } else if (nargs == 3) {
      return a + b + c;
    }
  }