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The MPL Reference Manual: pop_front
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pop_front

Synopsis

template<
      typename Sequence
    >
struct pop_front
{
    typedef unspecified type;
};

Description

pop_front performs a removal at the beginning of the sequence with guaranteed O(1) complexity.

Parameters

Parameter Requirement Description
Sequence Front Extensible Sequence A sequence to erase the first element from.

Expression semantics

For any Front Extensible Sequence s:

typedef pop_front::type r;
Return type:Front Extensible Sequence.
Precondition:empty::value == false.
Semantics:Equivalent to erasebegin::type>::type;.
Postcondition:size::value == size::value - 1.

Complexity

Amortized constant time.

Example

typedef vector::type types1;
typedef vector::type types2;
typedef vector::type types3;

typedef pop_front::type result1;
typedef pop_front::type result2;
typedef pop_front::type result3;

BOOST_MPL_ASSERT_RELATION( size::value, ==, 0 );
BOOST_MPL_ASSERT_RELATION( size::value, ==, 1 );
BOOST_MPL_ASSERT_RELATION( size::value, ==, 2 );

BOOST_MPL_ASSERT(( is_same< front::type, long > ));
BOOST_MPL_ASSERT(( is_same< front::type, int > ));
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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)