The elements of the library are defined in the boost::metaparse::v1 namespace. For example the one_char class is boost::metaparse::v1::one_char and is available after including the <boost/metaparse/v1/one_char.hpp> header file.

At the same time the library provides the <boost/metaparse/one_char.hpp> header file which includes <boost/metaparse/v1/one_char.hpp> and contains the following:

namespace boost
{
  namespace metaparse
  {
    using v1::one_char;
  }
}

This makes it possible to use one_char as boost::metaparse::one_char.

Future versions of the library may provide other namespaces (eg. v2). The header files in <boost/metaparse/...> provide the latest version of the library. To always get version v1, one should use header files in <boost/metaparse/v1/...>.

The library does not use inline namespaces to work on compilers that do not support them.