| .. Algorithms/Iteration Algorithms//iter_fold |
| |
| iter_fold |
| ========= |
| |
| Synopsis |
| -------- |
| |
| .. parsed-literal:: |
| |
| template< |
| typename Sequence |
| , typename State |
| , typename ForwardOp |
| > |
| struct iter_fold |
| { |
| typedef |unspecified| type; |
| }; |
| |
| |
| |
| Description |
| ----------- |
| |
| Returns the result of the successive application of binary ``ForwardOp`` to the result |
| of the previous ``ForwardOp`` invocation (``State`` if it's the first call) and each |
| iterator in the range [``begin<Sequence>::type``, ``end<Sequence>::type``) in order. |
| |
| |
| Header |
| ------ |
| |
| .. parsed-literal:: |
| |
| #include <boost/mpl/iter_fold.hpp> |
| |
| |
| |
| Parameters |
| ---------- |
| |
| +---------------+-------------------------------+---------------------------------------------------+ |
| | Parameter | Requirement | Description | |
| +===============+===============================+===================================================+ |
| | ``Sequence`` | |Forward Sequence| | A sequence to iterate. | |
| +---------------+-------------------------------+---------------------------------------------------+ |
| | ``State`` | Any type | The initial state for the first ``ForwardOp`` | |
| | | | application. | |
| +---------------+-------------------------------+---------------------------------------------------+ |
| | ``ForwardOp`` | Binary |Lambda Expression| | The operation to be executed on forward | |
| | | | traversal. | |
| +---------------+-------------------------------+---------------------------------------------------+ |
| |
| |
| Expression semantics |
| -------------------- |
| |
| For any |Forward Sequence| ``s``, binary |Lambda Expression| ``op``, and an |
| arbitrary type ``state``: |
| |
| |
| .. parsed-literal:: |
| |
| typedef iter_fold<s,state,op>::type t; |
| |
| :Return type: |
| A type. |
| |
| :Semantics: |
| Equivalent to |
| |
| .. parsed-literal:: |
| |
| typedef begin<s>::type i\ :sub:`1`; |
| typedef apply<op,state,i\ :sub:`1`>::type state\ :sub:`1`; |
| typedef next<i\ :sub:`1`>::type i\ :sub:`2`; |
| typedef apply<op,state\ :sub:`1`,i\ :sub:`2`>::type state\ :sub:`2`; |
| |...| |
| typedef apply<op,state\ :sub:`n-1`,i\ :sub:`n`>::type state\ :sub:`n`; |
| typedef next<i\ :sub:`n`>::type last; |
| typedef state\ :sub:`n` t; |
| |
| where ``n == size<s>::value`` and ``last`` is identical to ``end<s>::type``; equivalent |
| to ``typedef state t;`` if ``empty<s>::value == true``. |
| |
| |
| |
| Complexity |
| ---------- |
| |
| Linear. Exactly ``size<s>::value`` applications of ``op``. |
| |
| |
| Example |
| ------- |
| |
| .. parsed-literal:: |
| |
| typedef vector_c<int,5,-1,0,7,2,0,-5,4> numbers; |
| typedef iter_fold< |
| numbers |
| , begin<numbers>::type |
| , if_< less< deref<_1>, deref<_2> >,_2,_1 > |
| >::type max_element_iter; |
| |
| BOOST_MPL_ASSERT_RELATION( deref<max_element_iter>::type::value, ==, 7 ); |
| |
| |
| |
| See also |
| -------- |
| |
| |Algorithms|, |reverse_iter_fold|, |fold|, |reverse_fold|, |copy| |
| |
| |
| .. 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) |
