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 an old version of boost. Click here for the latest Boost documentation.

Struct first

boost::xpressive::op::first — first is a PolymorphicFunctionObject for fetching the first element of a pair.

Synopsis

// In header: <boost/xpressive/regex_actions.hpp>


struct first {
  // member classes/structs/unions
  template<typename Sig> 
  struct result {
  };
  template<typename This, typename Pair> 
  struct result<This(Pair)> {
    // types
    typedef remove_reference< Pair >::type::first_type type;
  };

  // public member functions
  template<typename Pair> Pair::first_type operator()(Pair const &) const;
};

Description

`first` public member functions

template<typename Pair> Pair::first_type operator()(Pair const & p) const;

Parameters:

`p`	The pair from which to fetch the first element.

Returns:

p.first