Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is an older version of Boost and was released in 2018. The current version is 1.90.0.

http::basic_fields::value_type::value_type

Constructor (deleted)

value_type(
    value_type const&);