| .. Algorithms/Transformation Algorithms//unique |80 |
| |
| unique |
| ====== |
| |
| Synopsis |
| -------- |
| |
| .. parsed-literal:: |
| |
| template< |
| typename Seq |
| , typename Pred |
| , typename In = |unspecified| |
| > |
| struct unique |
| { |
| typedef |unspecified| type; |
| }; |
| |
| |
| Description |
| ----------- |
| |
| Returns a sequence of the initial elements of every subrange of the |
| original sequence ``Seq`` whose elements are all the same. |
| |
| |transformation algorithm disclaimer| |
| |
| Header |
| ------ |
| |
| .. parsed-literal:: |
| |
| #include <boost/mpl/unique.hpp> |
| |
| |
| Model of |
| -------- |
| |
| |Reversible Algorithm| |
| |
| |
| Parameters |
| ---------- |
| |
| +---------------+-----------------------------------+-------------------------------+ |
| | Parameter | Requirement | Description | |
| +===============+===================================+===============================+ |
| | ``Sequence`` | |Forward Sequence| | An original sequence. | |
| +---------------+-----------------------------------+-------------------------------+ |
| | ``Pred`` | Binary |Lambda Expression| | An equivalence relation. | |
| +---------------+-----------------------------------+-------------------------------+ |
| | ``In`` | |Inserter| | An inserter. | |
| +---------------+-----------------------------------+-------------------------------+ |
| |
| |
| Expression semantics |
| -------------------- |
| |
| |Semantics disclaimer...| |Reversible Algorithm|. |
| |
| For any |Forward Sequence| ``s``, a binary |Lambda Expression| ``pred``, |
| and an |Inserter| ``in``: |
| |
| |
| .. parsed-literal:: |
| |
| typedef unique<s,pred,in>::type r; |
| |
| :Return type: |
| A type. |
| |
| :Semantics: |
| If ``size<s>::value <= 1``, then equivalent to |
| |
| .. parsed-literal:: |
| |
| typedef copy<s,in>::type r; |
| |
| otherwise equivalent to |
| |
| .. parsed-literal:: |
| |
| typedef lambda<pred>::type p; |
| typedef lambda<in::operation>::type in_op; |
| typedef apply_wrap\ ``2``\< |
| in_op |
| , in::state |
| , front<types>::type |
| >::type in_state; |
| |
| typedef fold< |
| s |
| , pair< in_state, front<s>::type > |
| , eval_if< |
| apply_wrap\ ``2``\<p, second<_1>, _2> |
| , identity< first<_1> > |
| , apply_wrap\ ``2``\<in_op, first<_1>, _2> |
| > |
| >::type::first r; |
| |
| |
| Complexity |
| ---------- |
| |
| Linear. Performs exactly ``size<s>::value - 1`` applications of ``pred``, and at |
| most ``size<s>::value`` insertions. |
| |
| |
| Example |
| ------- |
| |
| .. parsed-literal:: |
| |
| typedef vector<int,float,float,char,int,int,int,double> types; |
| typedef vector<int,float,char,int,double> expected; |
| typedef unique< types, is_same<_1,_2> >::type result; |
| |
| BOOST_MPL_ASSERT(( equal< result,expected > )); |
| |
| |
| See also |
| -------- |
| |
| |Transformation Algorithms|, |Reversible Algorithm|, |reverse_unique|, |remove|, |copy_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) |
