/Src/Dependencies/Boost/libs/phoenix/doc/inside/placeholder.qbk

 1[/==============================================================================
 2    Copyright (C) 2001-2010 Joel de Guzman
 3    Copyright (C) 2001-2005 Dan Marsden
 4    Copyright (C) 2001-2010 Thomas Heller
 5
 6    Distributed under the Boost Software License, Version 1.0. (See accompanying
 7    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 8===============================================================================/]
 9
10
11[section Placeholder Unification]
12
13Phoenix uses `boost::is_placeholder` for recognizing placeholders:
14
15    template <typename T>
16    struct is_placeholder
17    {
18        static const int value = 0;
19    };
20
21To adapt your own placeholder, the nested value needs to be greater than 0
22for your types. This is done by specializing this trait.
23
24[endsect]