| .. Algorithms/Transformation Algorithms//copy_if |20 |
| |
| copy_if |
| ======= |
| |
| Synopsis |
| -------- |
| |
| .. parsed-literal:: |
| |
| template< |
| typename Sequence |
| , typename Pred |
| , typename In = |unspecified| |
| > |
| struct copy_if |
| { |
| typedef |unspecified| type; |
| }; |
| |
| |
| |
| Description |
| ----------- |
| |
| Returns a filtered copy of the original sequence containing the elements that satisfy |
| the predicate ``Pred``. |
| |
| |transformation algorithm disclaimer| |
| |
| Header |
| ------ |
| |
| .. parsed-literal:: |
| |
| #include <boost/mpl/copy_if.hpp> |
| |
| |
| Model of |
| -------- |
| |
| |Reversible Algorithm| |
| |
| |
| Parameters |
| ---------- |
| |
| +---------------+-------------------------------+-------------------------------+ |
| | Parameter | Requirement | Description | |
| +===============+===============================+===============================+ |
| | ``Sequence`` | |Forward Sequence| | A sequence to copy. | |
| +---------------+-------------------------------+-------------------------------+ |
| | ``Pred`` | Unary |Lambda Expression| | A copying condition. | |
| +---------------+-------------------------------+-------------------------------+ |
| | ``In`` | |Inserter| | An inserter. | |
| +---------------+-------------------------------+-------------------------------+ |
| |
| |
| Expression semantics |
| -------------------- |
| |
| |Semantics disclaimer...| |Reversible Algorithm|. |
| |
| For any |Forward Sequence| ``s``, an unary |Lambda Expression| ``pred``, and |
| an |Inserter| ``in``: |
| |
| |
| .. parsed-literal:: |
| |
| typedef copy_if<s,pred,in>::type r; |
| |
| |
| :Return type: |
| A type. |
| |
| :Semantics: |
| Equivalent to |
| |
| .. parsed-literal:: |
| |
| typedef lambda<pred>::type p; |
| typedef lambda<in::operation>::type op; |
| |
| typedef fold< |
| s |
| , in::state |
| , eval_if< |
| apply_wrap\ ``1``\<p,_2> |
| , apply_wrap\ ``2``\<op,_1,_2> |
| , identity<_1> |
| > |
| >::type r; |
| |
| |
| Complexity |
| ---------- |
| |
| Linear. Exactly ``size<s>::value`` applications of ``pred``, and at |
| most ``size<s>::value`` applications of ``in::operation``. |
| |
| |
| Example |
| ------- |
| |
| .. parsed-literal:: |
| |
| typedef copy_if< |
| range_c<int,0,10> |
| , less< _1, int_<5> > |
| , back_inserter< vector<> > |
| >::type result; |
| |
| BOOST_MPL_ASSERT_RELATION( size<result>::value, ==, 5 ); |
| BOOST_MPL_ASSERT(( equal<result,range_c<int,0,5> > )); |
| |
| |
| See also |
| -------- |
| |
| |Transformation Algorithms|, |Reversible Algorithm|, |reverse_copy_if|, |copy|, |remove_if|, |replace_if| |
| |
| |
| .. 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) |
