...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
namespace boost { class in_place_init_t { /* see below */ } ; const in_place_init_t in_place_init ( /* see below */ ) ; class in_place_init_if_t { /*see below*/ } ; const in_place_init_if_t in_place_init_if ( /*see below*/ ) ; }
Classes in_place_init_t
and in_place_init_if_t
are empty classes. Their purpose is to control overload resolution in the
initialization of optional objects. They are empty, trivially copyable
classes with disabled default constructor.