The usage of std::binary_function is really old legacy to define the functions used in STL algorithms like std::sort. std::binary_function was also removed from C++ with newer C++ versions. Switch to the modern implementation using lambdas in the STL algorithms. This also increase code readability since the code is located at the same place where it is used.
This MR should also test if the GitLab link in the Redmine issue is properly created again.