ceph/src/boost/libs/phoenix/doc/actors.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 [section Actor]
  11
  12 The `Actor` is the main concept behind the library. Actors are function objects.
  13 An actor can accept 0 to `BOOST_PHOENIX_LIMIT` arguments.
  14
  15 [note You can set `BOOST_PHOENIX_LIMIT`, the predefined maximum arity an
  16 actor can take. By default, `BOOST_PHOENIX_LIMIT` is set to 10.]
  17
  18 Phoenix supplies an `actor` class template whose specializations
  19 model the `Actor` concept.  `actor` has one template parameter, `Expr`,
  20 that supplies the underlying expression to evaluate.
  21
  22     template <typename Expr>
  23     struct actor
  24     {
  25         return_type
  26         operator()() const;
  27
  28         template <typename T0>
  29         return_type
  30         operator()(T0& _0) const;
  31
  32         template <typename T0, typename T1>
  33         return_type
  34         operator()(T0& _0, T1& _1) const;
  35
  36         //...
  37     };
  38
  39 The actor class accepts the arguments through a set of function call operators
  40 for 0 to `BOOST_PHOENIX_LIMIT` arities (Don't worry about the details, for now. Note, for example,
  41 that we skimp over the details regarding `return_type`). The arguments are passed through to
  42 the evaluation mechanism. For more information see [link phoenix.inside.actor Inside Actors].
  43
  44 [endsect]
  45