- vertex* copy() const { return new Sigma_flipped(*this); }
- ijpair get_increment() const { return ijpair(0, indices.first+indices.second+1); }
- const ex evaluate(const symbol &x, const unsigned grad) const { return Sigma::evaluate(x, grad); }
+ vertex* copy() const override { return new Sigma_flipped(*this); }
+ ijpair get_increment() const override { return ijpair(0, indices.first+indices.second+1); }
+ const ex evaluate(const symbol &x, const unsigned grad) const override { return Sigma::evaluate(x, grad); }