| .. Algorithms/Runtime Algorithms//for_each |10 |
| |
| for_each |
| ======== |
| |
| Synopsis |
| -------- |
| |
| .. parsed-literal:: |
| |
| template< |
| typename Sequence |
| , typename F |
| > |
| void for_each( F f ); |
| |
| template< |
| typename Sequence |
| , typename TransformOp |
| , typename F |
| > |
| void for_each( F f ); |
| |
| |
| Description |
| ----------- |
| |
| ``for_each`` is a family of overloaded function templates: |
| |
| * ``for_each<Sequence>( f )`` applies the runtime function object |
| ``f`` to every element in the |begin/end<Sequence>| range. |
| |
| * ``for_each<Sequence,TransformOp>( f )`` applies the runtime function |
| object ``f`` to the result of the transformation ``TransformOp`` of |
| every element in the |begin/end<Sequence>| range. |
| |
| |
| Header |
| ------ |
| |
| .. parsed-literal:: |
| |
| #include <boost/mpl/for_each.hpp> |
| |
| |
| Parameters |
| ---------- |
| |
| +-------------------+-----------------------------------+-----------------------------------+ |
| | Parameter | Requirement | Description | |
| +===================+===================================+===================================+ |
| | ``Sequence`` | |Forward Sequence| | A sequence to iterate. | |
| +-------------------+-----------------------------------+-----------------------------------+ |
| | ``TransformOp`` | |Lambda Expression| | A transformation. | |
| +-------------------+-----------------------------------+-----------------------------------+ |
| | ``f`` | An |unary function object| | A runtime operation to apply. | |
| +-------------------+-----------------------------------+-----------------------------------+ |
| |
| |
| Expression semantics |
| -------------------- |
| |
| For any |Forward Sequence| ``s``, |Lambda Expression| ``op`` , and an |
| |unary function object| ``f``: |
| |
| .. parsed-literal:: |
| |
| for_each<s>( f ); |
| |
| :Return type: |
| ``void`` |
| |
| :Postcondition: |
| Equivalent to |
| |
| .. parsed-literal:: |
| |
| typedef begin<Sequence>::type i\ :sub:`1`; |
| |value_initialized|\ < deref<i\ :sub:`1`>::type > x\ :sub:`1`; |
| f(boost::get(x\ :sub:`1`)); |
| |
| typedef next<i\ :sub:`1`>::type i\ :sub:`2`; |
| |value_initialized|\ < deref<i\ :sub:`2`>::type > x\ :sub:`2`; |
| f(boost::get(x\ :sub:`2`)); |
| |...| |
| |value_initialized|\ < deref<i\ :sub:`n`>::type > x\ :sub:`n`; |
| f(boost::get(x\ :sub:`n`)); |
| typedef next<i\ :sub:`n`>::type last; |
| |
| where ``n == size<s>::value`` and ``last`` is identical to |
| ``end<s>::type``; no effect if ``empty<s>::value == true``. |
| |
| |
| .. parsed-literal:: |
| |
| for_each<s,op>( f ); |
| |
| :Return type: |
| ``void`` |
| |
| :Postcondition: |
| Equivalent to |
| |
| .. parsed-literal:: |
| |
| for_each< transform_view<s,op> >( f ); |
| |
| |
| Complexity |
| ---------- |
| |
| Linear. Exactly ``size<s>::value`` applications of ``op`` and ``f``. |
| |
| |
| Example |
| ------- |
| |
| .. parsed-literal:: |
| |
| struct value_printer |
| { |
| template< typename U > void operator()(U x) |
| { |
| std::cout << x << '\\n'; |
| } |
| }; |
| |
| int main() |
| { |
| for_each< range_c<int,0,10> >( value_printer() ); |
| } |
| |
| |
| See also |
| -------- |
| |
| |Runtime Algorithms|, |Views|, |transform_view| |
| |
| .. |unary function object| replace:: `unary function object <http://www.sgi.com/tech/stl/UnaryFunction.html>`__ |
| .. |value_initialized| replace:: `value_initialized <http://www.boost.org/libs/utility/value_init.htm>`__ |
| |
| |
| .. 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) |