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 2017. The current version is 1.89.0.
boost::proto::callable — Base class for callable PolymorphicFunctionObjects
// In header: <boost/proto/proto_fwd.hpp> struct callable { };
When defining a callable PolymorphicFunctionObject, inherit
from proto::callable so that it can be used to create
a CallableTransform.
proto::is_callable<T>::value is
true for types that inherit from
proto::callable.