在Eigen中有没有等同于triu_indices (numpy)的东西？

#include <iostream>
#include <Eigen/Dense>

int main() {
    Eigen::MatrixXd matrix(3, 3);
    matrix << 1, 2, 3,
              4, 5, 6,
              7, 8, 9;

    std::vector<std::pair<int, int>> indices;
    for (int i = 0; i < matrix.rows(); ++i) {
        for (int j = i; j < matrix.cols(); ++j) {
            indices.push_back(std::make_pair(i, j));
        }
    }

    std::cout << "Upper triangular indices:" << std::endl;
    for (const auto& index : indices) {
        std::cout << "(" << index.first << ", " << index.second << ")" << std::endl;
    }

    return 0;
}