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

Struct template result

boost::proto::expr::result

template<typename Signature> 
struct result {
  // types
  typedef unspecified type;
};

Encodes the return type of expr<>::operator(). Makes expr<> a TR1-style function object type usable with boost::result_of<>