...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
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Front Page / Sequences / Intrinsic Metafunctions / pop_front |
pop_front performs a removal at the beginning of the sequence with guaranteed O(1) complexity.
#include <boost/mpl/pop_front.hpp>
Parameter | Requirement | Description |
---|---|---|
Sequence | Front Extensible Sequence | A sequence to erase the first element from. |
For any Front Extensible Sequence s:
typedef pop_front<s>::type r;
Return type: | Front Extensible Sequence. |
---|---|
Precondition: | empty<s>::value == false. |
Semantics: | Equivalent to erase<s,begin<s>::type>::type;. |
Postcondition: | size<r>::value == size<s>::value - 1. |
Amortized constant time.
typedef vector<long>::type types1; typedef vector<int,long>::type types2; typedef vector<char,int,long>::type types3; typedef pop_front<types1>::type result1; typedef pop_front<types2>::type result2; typedef pop_front<types3>::type result3; BOOST_MPL_ASSERT_RELATION( size<result1>::value, ==, 0 ); BOOST_MPL_ASSERT_RELATION( size<result2>::value, ==, 1 ); BOOST_MPL_ASSERT_RELATION( size<result3>::value, ==, 2 ); BOOST_MPL_ASSERT(( is_same< front<result2>::type, long > )); BOOST_MPL_ASSERT(( is_same< front<result3>::type, int > ));