With recent versions of C++, it is possible to have constexpr iterators, for example for std::array (and in c++20 for vector and string).
The boost iterator functionality, like transform_iterator, filter_iterator ... ain't constexpr and as a result can't be used at constexpr time.
With recent versions of C++, it is possible to have constexpr iterators, for example for std::array (and in c++20 for vector and string).
The boost iterator functionality, like transform_iterator, filter_iterator ... ain't constexpr and as a result can't be used at constexpr time.