| .. Iterators/Iterator Metafunctions//advance |10 |
| |
| advance |
| ======= |
| |
| Synopsis |
| -------- |
| |
| .. parsed-literal:: |
| |
| template< |
| typename Iterator |
| , typename N |
| > |
| struct advance |
| { |
| typedef |unspecified| type; |
| }; |
| |
| |
| |
| Description |
| ----------- |
| |
| Moves ``Iterator`` by the distance ``N``. For |bidirectional| and |
| |random access| iterators, the distance may be negative. |
| |
| |
| Header |
| ------ |
| |
| .. parsed-literal:: |
| |
| #include <boost/mpl/advance.hpp> |
| |
| |
| Parameters |
| ---------- |
| |
| +---------------+---------------------------+-----------------------------------+ |
| | Parameter | Requirement | Description | |
| +===============+===========================+===================================+ |
| | ``Iterator`` | |Forward Iterator| | An iterator to advance. | |
| +---------------+---------------------------+-----------------------------------+ |
| | ``N`` | |Integral Constant| | A distance. | |
| +---------------+---------------------------+-----------------------------------+ |
| |
| |
| Model Of |
| -------- |
| |
| |Tag Dispatched Metafunction| |
| |
| |
| Expression semantics |
| -------------------- |
| |
| For a |Forward Iterator| ``iter`` and arbitrary |Integral Constant| ``n``: |
| |
| .. parsed-literal:: |
| |
| typedef advance<iter,n>::type j; |
| |
| :Return type: |
| |Forward Iterator|. |
| |
| :Precondition: |
| If ``Iterator`` is a |Forward Iterator|, ``n::value`` must be nonnegative. |
| |
| :Semantics: |
| Equivalent to: |
| |
| .. parsed-literal:: |
| |
| typedef iter i0; |
| typedef next<i0>::type i1; |
| |...| |
| typedef next<i\ *n-1*\ >::type j; |
| |
| if ``n::value > 0``, and |
| |
| .. parsed-literal:: |
| |
| typedef iter i0; |
| typedef prior<i0>::type i1; |
| |...| |
| typedef prior<i\ *n-1*\ >::type j; |
| |
| otherwise. |
| |
| |
| :Postcondition: |
| ``j`` is dereferenceable or past-the-end; |
| ``distance<iter,j>::value == n::value`` if ``n::value > 0``, and |
| ``distance<j,iter>::value == n::value`` otherwise. |
| |
| |
| Complexity |
| ---------- |
| |
| Amortized constant time if ``iter`` is a model of |
| |Random Access Iterator|, otherwise linear time. |
| |
| |
| Example |
| ------- |
| |
| .. parsed-literal:: |
| |
| typedef range_c<int,0,10> numbers; |
| typedef begin<numbers>::type first; |
| typedef end<numbers>::type last; |
| |
| typedef advance<first,int_<10> >::type i1; |
| typedef advance<last,int_<-10> >::type i2; |
| |
| BOOST_MPL_ASSERT(( boost::is_same<i1,last> )); |
| BOOST_MPL_ASSERT(( boost::is_same<i2,first> )); |
| |
| |
| See also |
| -------- |
| |
| |Iterators|, |Tag Dispatched Metafunction|, |distance|, |next| |
| |
| .. |bidirectional| replace:: `bidirectional`_ |
| .. _bidirectional: `Bidirectional Iterator`_ |
| .. |random access| replace:: `random access`_ |
| .. _random access: `Random Access Iterator`_ |
| |
| |
| .. 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) |