| <html> |
| <head> |
| <title>Header </title> |
| <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> |
| <meta name="Template" content="C:\PROGRAM FILES\MICROSOFT OFFICE\OFFICE\html.dot"> |
| <meta name="GENERATOR" content="Microsoft FrontPage 5.0"> |
| <boostcompressed_pair.hpp> |
| </head> |
| <body bgcolor="#ffffff" text="#000000" link="#0000ff" vlink="#800080"> |
| <h2><img src="../../boost.png" width="276" height="86">Header <<a href="../../boost/detail/compressed_pair.hpp">boost/compressed_pair.hpp</a>></h2> |
| <p>All of the contents of <boost/compressed_pair.hpp> are defined inside |
| namespace boost.</p> |
| <p>The class compressed pair is very similar to std::pair, but if either of the |
| template arguments are empty classes, then the "empty base-class optimisation" |
| is applied to compress the size of the pair.</p> |
| <pre>template <class T1, class T2> |
| class compressed_pair |
| { |
| public: |
| typedef T1 first_type; |
| typedef T2 second_type; |
| typedef typename call_traits<first_type>::param_type first_param_type; |
| typedef typename call_traits<second_type>::param_type second_param_type; |
| typedef typename call_traits<first_type>::reference first_reference; |
| typedef typename call_traits<second_type>::reference second_reference; |
| typedef typename call_traits<first_type>::const_reference first_const_reference; |
| typedef typename call_traits<second_type>::const_reference second_const_reference; |
| |
| compressed_pair() : base() {} |
| compressed_pair(first_param_type x, second_param_type y); |
| explicit compressed_pair(first_param_type x); |
| explicit compressed_pair(second_param_type y); |
| |
| compressed_pair& operator=(const compressed_pair&); |
| |
| first_reference first(); |
| first_const_reference first() const; |
| |
| second_reference second(); |
| second_const_reference second() const; |
| |
| void swap(compressed_pair& y); |
| };</pre> |
| <p>The two members of the pair can be accessed using the member functions first() |
| and second(). Note that not all member functions can be instantiated for all |
| template parameter types. In particular compressed_pair can be instantiated for |
| reference and array types, however in these cases the range of constructors |
| that can be used are limited. If types T1 and T2 are the same type, then there |
| is only one version of the single-argument constructor, and this constructor |
| initialises both values in the pair to the passed value.</p> |
| <P>Note that if either member is a POD type, then that member is not |
| zero-initialized by the compressed_pair default constructor: it's up to you to |
| supply an initial value for these types if you want them to have a default |
| value.</P> |
| <p>Note that compressed_pair can not be instantiated if either of the template |
| arguments is a union type, unless there is compiler support for |
| boost::is_union, or if boost::is_union is specialised for the union type.</p> |
| <p>Finally, a word of caution for Visual C++ 6 users: if either argument is an |
| empty type, then assigning to that member will produce memory corruption, |
| unless the empty type has a "do nothing" assignment operator defined. This is |
| due to a bug in the way VC6 generates implicit assignment operators.</p> |
| <h3>Acknowledgements</h3> |
| <p>Based on contributions by Steve Cleary, Beman Dawes, Howard Hinnant and John |
| Maddock.</p> |
| <p>Maintained by <a href="mailto:john@johnmaddock.co.uk">John Maddock</a>, the |
| latest version of this file can be found at <a href="http://www.boost.org">www.boost.org</a>, |
| and the boost discussion list at <a href="http://www.yahoogroups.com/list/boost">www.yahoogroups.com/list/boost</a>.</p> |
| <hr> |
| <p>Revised |
| <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%d %B %Y" startspan -->07 November 2007<!--webbot bot="Timestamp" endspan i-checksum="40338" --></p> |
| <p>© Copyright Beman Dawes, 2000.</p> |
| <p>Distributed under the Boost Software License, Version 1.0. See |
| <a href="http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a></p> |
| |
| </body> |
| </html> |
