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 the documentation for a snapshot of the master branch, built from commit 937c0286ac.

Struct template is_expr

boost::proto::is_expr — A Boolean metafunction that indicates whether a given type T is a Proto expression type.

Synopsis

// In header: <boost/proto/traits.hpp>

template<typename T> 
struct is_expr :  mpl::bool_<true-or-false> {
};

Description

If T is an instantiation of proto::expr<> or proto::basic_expr<> or is an extension (via proto::extends<> or BOOST_PROTO_EXTENDS()) of such an instantiation, proto::is_expr<T>::value is true. Otherwise, proto::is_expr<T>::value is false.