CppCoreGuidelines T.24 通过 tag 标签类或 traits 区分语义不同的概念

template<typename I>    // iterator providing random access
// Note: random_access_iterator is defined in <iterator>
concept RA_iter = ...;

template<typename I>    // iterator providing random access to contiguous data
// Note: contiguous_iterator is defined in <iterator>
concept Contiguous_iter =
    RA_iter<I> && is_contiguous_v<I>;  // using is_contiguous trait

template<typename I> concept Contiguous = is_contiguous_v<I>;

template<typename I>
concept Contiguous_iter = RA_iter<I> && Contiguous<I>;