| .. Metafunctions/Composition and Argument Binding//bind |30 |
| |
| bind |
| ==== |
| |
| Synopsis |
| -------- |
| |
| .. parsed-literal:: |
| |
| template< |
| typename F |
| > |
| struct bind0 |
| { |
| // |unspecified| |
| // |...| |
| }; |
| |
| template< |
| typename F, typename A1 |
| > |
| struct bind1 |
| { |
| // |unspecified| |
| // |...| |
| }; |
| |
| |...| |
| |
| template< |
| typename F, typename A1,\ |...| typename An |
| > |
| struct bind\ *n* |
| { |
| // |unspecified| |
| // |...| |
| }; |
| |
| template< |
| typename F |
| , typename A1 = |unspecified| |
| |...| |
| , typename An = |unspecified| |
| > |
| struct bind |
| { |
| // |unspecified| |
| // |...| |
| }; |
| |
| |
| Description |
| ----------- |
| |
| ``bind`` is a higher-order primitive for |Metafunction Class| composition |
| and argument binding. In essence, it's a compile-time counterpart of |
| the similar run-time functionality provided by |Boost.Bind| and |Boost.Lambda| |
| libraries. |
| |
| |
| Header |
| ------ |
| |
| .. parsed-literal:: |
| |
| #include <boost/mpl/bind.hpp> |
| |
| |
| Model of |
| -------- |
| |
| |Metafunction Class| |
| |
| |
| Parameters |
| ---------- |
| |
| +---------------+-----------------------------------+-----------------------------------------------+ |
| | Parameter | Requirement | Description | |
| +===============+===================================+===============================================+ |
| | ``F`` | |Metafunction Class| | An metafunction class to perform binding on. | |
| +---------------+-----------------------------------+-----------------------------------------------+ |
| | |A1...An| | Any type | Arguments to bind. | |
| +---------------+-----------------------------------+-----------------------------------------------+ |
| |
| |
| Expression semantics |
| -------------------- |
| |
| For any |Metafunction Class| ``f`` and arbitrary types |a1...an|: |
| |
| .. parsed-literal:: |
| |
| typedef bind<f,a1,...a\ *n*\ > g; |
| typedef bind\ *n*\ <f,a1,...a\ *n*\ > g; |
| |
| :Return type: |
| |Metafunction Class| |
| |
| .. _`bind semantics`: |
| |
| :Semantics: |
| Equivalent to |
| |
| .. parsed-literal:: |
| |
| struct g |
| { |
| template< |
| typename U1 = |unspecified| |
| |...| |
| , typename U\ *n* = |unspecified| |
| > |
| struct apply |
| : apply_wrap\ *n*\ < |
| typename h0<f,U1,\ |...|\ U\ *n*>::type |
| , typename h1<a1,U1,\ |...|\ U\ *n*>::type |
| |...| |
| , typename h\ *n*\ <a\ *n*\ ,U1,\ |...|\ U\ *n*>::type |
| > |
| { |
| }; |
| }; |
| |
| where ``h``\ *k* is equivalent to |
| |
| .. parsed-literal:: |
| |
| template< typename X, typename U1,\ |...| typename U\ *n* > struct h\ *k* |
| : apply_wrap\ *n*\ <X,U1,\ |...|\ U\ *n*> |
| { |
| }; |
| |
| if ``f`` or ``a``\ *k* is a |bind expression| or a |placeholder|, and |
| |
| .. parsed-literal:: |
| |
| template< typename X, typename U1,\ |...| typename U\ *n* > struct h\ *k* |
| { |
| typedef X type; |
| }; |
| |
| otherwise. |Note:| Every ``n``\th appearance of the `unnamed placeholder`__ |
| in the ``bind<f,a1,...an>`` specialization is replaced with the corresponding |
| numbered placeholder ``_``\ *n* |-- end note| |
| |
| __ `Placeholders`_ |
| |
| |
| Example |
| ------- |
| |
| .. parsed-literal:: |
| |
| struct f1 |
| { |
| template< typename T1 > struct apply |
| { |
| typedef T1 type; |
| }; |
| }; |
| |
| struct f5 |
| { |
| template< typename T1, typename T2, typename T3, typename T4, typename T5 > |
| struct apply |
| { |
| typedef T5 type; |
| }; |
| }; |
| |
| typedef apply_wrap\ ``1``\< |
| bind\ ``1``\<f1,_1> |
| , int |
| >::type r11; |
| |
| typedef apply_wrap\ ``5``\< |
| bind\ ``1``\<f1,_5> |
| , void,void,void,void,int |
| >::type r12; |
| |
| BOOST_MPL_ASSERT(( is_same<r11,int> )); |
| BOOST_MPL_ASSERT(( is_same<r12,int> )); |
| |
| typedef apply_wrap\ ``5``\< |
| bind\ ``5``\<f5,_1,_2,_3,_4,_5> |
| , void,void,void,void,int |
| >::type r51; |
| |
| typedef apply_wrap\ ``5``\< |
| bind\ ``5``\<f5,_5,_4,_3,_2,_1> |
| , int,void,void,void,void |
| >::type r52; |
| |
| BOOST_MPL_ASSERT(( is_same<r51,int> )); |
| BOOST_MPL_ASSERT(( is_same<r52,int> )); |
| |
| |
| See also |
| -------- |
| |
| |Composition and Argument Binding|, |Invocation|, |Placeholders|, |lambda|, |quote|, |
| |protect|, |apply|, |apply_wrap| |
| |
| |
| .. 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) |
