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 2013. The current version is 1.89.0.
These traits are all value traits, which is to say the
traits classes all inherit from integral_constant,
and are used to access some numerical property of a type. Often this is a
simple true or false Boolean value, but in a few cases may be some other
integer value (for example when dealing with type alignments, or array bounds:
see alignment_of,
rank
and extent).