ceph/src/boost/libs/mpl/doc/src/refmanual/unpack_args.rst

   1 .. Metafunctions/Invocation//unpack_args |30
   2
   3 unpack_args
   4 ===========
   5
   6 Synopsis
   7 --------
   8
   9 .. parsed-literal::
  10
  11     template<
  12           typename F
  13         >
  14     struct unpack_args
  15     {
  16         // |unspecified|
  17         // |...|
  18     };
  19
  20
  21 Description
  22 -----------
  23
  24 A higher-order primitive transforming an *n*-ary |Lambda Expression| ``F`` into
  25 an unary |Metafunction Class| ``g`` accepting a single sequence of *n* arguments.
  26
  27
  28 Header
  29 ------
  30
  31 .. parsed-literal::
  32
  33     #include <boost/mpl/unpack_args.hpp>
  34
  35
  36 Model of
  37 --------
  38
  39 |Metafunction Class|
  40
  41
  42 Parameters
  43 ----------
  44
  45 +---------------+-----------------------+-------------------------------------------+
  46 | Parameter     | Requirement           | Description                               |
  47 +===============+=======================+===========================================+
  48 | ``F``         | |Lambda Expression|   | A lambda expression to adopt.             |
  49 +---------------+-----------------------+-------------------------------------------+
  50
  51
  52 Expression semantics
  53 --------------------
  54
  55 For an arbitrary |Lambda Expression| ``f``, and arbitrary types |a1...an|:
  56
  57
  58 .. parsed-literal::
  59
  60     typedef unpack_args<f> g;
  61
  62 :Return type:
  63     |Metafunction Class|.
  64
  65 :Semantics:
  66     ``g`` is a unary |Metafunction Class| such that
  67
  68     .. parsed-literal::
  69
  70         apply_wrap\ *n*\ < g, vector<a1,\ |...|\ a\ *n*\ > >::type
  71
  72     is identical to
  73
  74     .. parsed-literal::
  75
  76         apply<F,a1,\ |...|\ a\ *n*\ >::type
  77
  78
  79 Example
  80 -------
  81
  82 .. parsed-literal::
  83
  84     BOOST_MPL_ASSERT(( apply<
  85           unpack_args< is_same<_1,_2> >
  86         , vector<int,int>
  87         > ));
  88
  89
  90 See also
  91 --------
  92
  93 |Metafunctions|, |Lambda Expression|, |Metafunction Class|, |apply|, |apply_wrap|, |bind|
  94
  95
  96 .. copyright:: Copyright ©  2001-2009 Aleksey Gurtovoy and David Abrahams
  97    Distributed under the Boost Software License, Version 1.0. (See accompanying
  98    file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)