...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
boost::xpressive::op::at
// In header: <boost/xpressive/regex_actions.hpp> struct at { // member classes/structs/unions template<typename Sig> struct result { }; template<typename This, typename Cont, typename Idx> struct result<This(Cont &, Idx)> : public mpl::if_c< is_const< Cont >::value, Cont::const_reference, Cont::reference > { }; template<typename This, typename Cont, typename Idx> struct result<This(Cont, Idx)> : public boost::xpressive::op::at::result< This(Cont const &, Idx)> { }; // public member functions template<typename Cont, typename Idx> Cont::reference operator()(Cont &, Idx idx ) const; template<typename Cont, typename Idx> Cont::const_reference operator()(Cont const &, Idx) const; };