ceph/src/boost/libs/convert/include/boost/make_default.hpp

   1 /// @file
   2 // Copyright (c) 2009-2016 Vladimir Batov.
   3 // Use, modification and distribution are subject to the Boost Software License,
   4 // Version 1.0. See http://www.boost.org/LICENSE_1_0.txt.
   5
   6 #ifndef BOOST_MAKE_DEFAULT_HPP
   7 #define BOOST_MAKE_DEFAULT_HPP
   8
   9 namespace boost
  10 {
  11     /// @details A considerable number of libraries require an instance of a class
  12     /// provided (storage created and initialized). For example,
  13     /// @code
  14     ///    Type result;
  15     ///    ...
  16     ///    istream >> result;
  17     /// @endcode
  18     /// In generic code that results in the Default Constructibility requirement imposed
  19     /// on every type 'Type' to be used with the respective code. Inevitably, that requirement
  20     /// a) either excludes all the classes that for various reasons do not meet that requirement or
  21     /// b) imposes certain (not necessarily desirable) design/implementation onto respective classes.
  22     ///
  23     /// Deployment of boost::make_default() eliminates the Default Constructibility requirement with
  24     /// @code
  25     ///    Type result = boost::make_default<Type>();
  26     ///    ...
  27     ///    istream >> result;
  28     /// @endcode
  29     /// Classes with no default constructor can now be included via a boost::make_default() specialization:
  30     /// @code
  31     /// namespace boost
  32     /// {
  33     ///     template<> inline Type make_default<Type>() { return Type(parameters); }
  34     /// }
  35     /// @endcode
  36
  37     template<typename T> T make_default() { return T(); }
  38 }
  39
  40 #endif // BOOST_MAKE_DEFAULT_HPP