.. Metafunctions/Invocation//apply |10

apply

Synopsis

.. parsed-literal::

template< 
      typename F
    >
struct apply0
{
    typedef |unspecified| type;
};

template< 
      typename F, typename A1
    >
struct apply1
{
    typedef |unspecified| type;
};

|...|

template< 
      typename F, typename A1,\ |...| typename An
    >
struct apply\ *n*
{
    typedef |unspecified| type;
};

template< 
      typename F
    , typename A1 = |unspecified|
    |...|
    , typename An = |unspecified|
    >
struct apply
{
    typedef |unspecified| type;
};

Description

Invokes a |Metafunction Class| or a |Lambda Expression| F with arguments A1,... An.

Header

.. parsed-literal::

#include <boost/mpl/apply.hpp>

Parameters

+---------------+-----------------------------------+-----------------------------------------------+ | Parameter | Requirement | Description | +===============+===================================+===============================================+ | F | |Lambda Expression| | An expression to invoke. | +---------------+-----------------------------------+-----------------------------------------------+ | |A1...An| | Any type | Invocation arguments. | +---------------+-----------------------------------+-----------------------------------------------+

Expression semantics

For any |Lambda Expression| f and arbitrary types a1,... an:

.. parsed-literal::

typedef apply\ *n*\<f,a1,\ |...|\ a\ *n*\>::type t;
typedef apply<f,a1,\ |...|\ a\ *n*\>::type t;

:Return type: Any type.

:Semantics: Equivalent to typedef apply_wrap\ n\ < lambda<f>::type,a1,... an>::type t;.

Example

.. parsed-literal::

template< typename N1, typename N2 > struct int_plus
    : int_<( N1::value + N2::value )>
{
};

typedef apply< int_plus<_1,_2>, int_<2>, int_<3> >::type r1;
typedef apply< quote\ ``2``\ <int_plus>, int_<2>, int_<3> >::type r2;

BOOST_MPL_ASSERT_RELATION( r1::value, ==, 5 );
BOOST_MPL_ASSERT_RELATION( r2::value, ==, 5 );

See also

|Metafunctions|, |apply_wrap|, |lambda|, |quote|, |bind|

.. copyright:: Copyright 2001-2009 Aleksey Gurtovoy and David Abrahams Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)