- size_t nops() const { return 0; }
- ex op(size_t i) const { return inherited::op(i); }
- ex operator[](const ex & index) const { return inherited::operator[](index); }
- ex operator[](size_t i) const { return inherited::operator[](i); }
- ex & let_op(size_t i) { return inherited::let_op(i); }
- ex & operator[](const ex & index) { return inherited::operator[](index); }
- ex & operator[](size_t i) { return inherited::operator[](i); }
+ size_t nops() const override { return 0; }
+ ex op(size_t i) const override { return inherited::op(i); }
+ ex operator[](const ex & index) const override { return inherited::operator[](index); }
+ ex operator[](size_t i) const override { return inherited::operator[](i); }
+ ex & let_op(size_t i) override { return inherited::let_op(i); }
+ ex & operator[](const ex & index) override { return inherited::operator[](index); }
+ ex & operator[](size_t i) override { return inherited::operator[](i); }