105 lines
2.1 KiB
ReStructuredText
105 lines
2.1 KiB
ReStructuredText
.. Sequences/Intrinsic Metafunctions//pop_back
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pop_back
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========
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Synopsis
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--------
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.. parsed-literal::
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template<
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typename Sequence
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>
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struct pop_back
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{
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typedef |unspecified| type;
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};
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Description
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-----------
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``pop_back`` performs a removal at the end of the sequence with guaranteed |O(1)|
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complexity.
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Header
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------
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.. parsed-literal::
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#include <boost/mpl/pop_back.hpp>
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Model of
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--------
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|Tag Dispatched Metafunction|
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Parameters
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----------
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+---------------+-------------------------------+-----------------------------------------------+
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| Parameter | Requirement | Description |
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+===============+===============================+===============================================+
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| ``Sequence`` | |Back Extensible Sequence| | A sequence to erase the last element from. |
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+---------------+-------------------------------+-----------------------------------------------+
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Expression semantics
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--------------------
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For any |Back Extensible Sequence| ``s``:
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.. parsed-literal::
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typedef pop_back<s>::type r;
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:Return type:
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|Back Extensible Sequence|.
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:Precondition:
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``empty<s>::value == false``.
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:Semantics:
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Equivalent to ``erase<s,end<s>::type>::type;``.
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:Postcondition:
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``size<r>::value == size<s>::value - 1``.
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Complexity
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----------
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Amortized constant time.
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Example
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-------
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.. parsed-literal::
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typedef vector<long>::type types1;
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typedef vector<long,int>::type types2;
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typedef vector<long,int,char>::type types3;
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typedef pop_back<types1>::type result1;
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typedef pop_back<types2>::type result2;
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typedef pop_back<types3>::type result3;
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BOOST_MPL_ASSERT_RELATION( size<result1>::value, ==, 0 );
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BOOST_MPL_ASSERT_RELATION( size<result2>::value, ==, 1 );
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BOOST_MPL_ASSERT_RELATION( size<result3>::value, ==, 2 );
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BOOST_MPL_ASSERT(( is_same< back<result2>::type, long> ));
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BOOST_MPL_ASSERT(( is_same< back<result3>::type, int > ));
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See also
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--------
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|Back Extensible Sequence|, |erase|, |push_back|, |back|, |pop_front|
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