ceph/src/boost/libs/phoenix/doc/actor.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         return_type
  29         operator()();
  30
  31         template <typename T0>
  32         return_type
  33         operator()(T0& _0) const;
  34
  35         template <typename T0>
  36         return_type
  37         operator()(T0 const& _0) const;
  38
  39         template <typename T0>
  40         return_type
  41         operator()(T0& _0);
  42
  43         template <typename T0>
  44         return_type
  45         operator()(T0 const& _0);
  46
  47
  48         //...
  49     };
  50
  51 The actor class accepts the arguments through a set of function call operators
  52 for 0 to `BOOST_PHOENIX_LIMIT` arities (Don't worry about the details, for now. Note, for example,
  53 that we skimed over the details regarding `return_type`). The arguments
  54 are then forwarded to the actor's `Expr` for evaluation.
  55
  56 [endsect]
  57