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[Home]push_front

Synopsis

template<
      typename Sequence
    , typename T
    >
struct push_front
{
    typedef unspecified type;
};

Description

push_front performs an insertion at the beginning of the sequence. The algorithm returns a new sequence which contains type T as its first element. The result sequence preserves all the functional and performance characteristics of the original Sequence, except its size and identity.

Definition

#include "boost/mpl/push_front.hpp"

Parameters

 Parameter  Requirement  Description  
SequenceA model of Extensible SequenceA sequence to handle the insert operation.
TA typeThe element to be inserted.

Expression semantics

 Expression  Expression type  Precondition  Semantics  Postcondition 
typedef push_front<Sequence,T>::type s;A model of Extensible SequenceEquivalent to typedef insert< Sequence,begin<Sequence>::type,T >::type s;size<s>::type::value == size<Sequence>::type::value + 1; front<s>::type is identical to T

Complexity

Amortized constant time [1].

Example

typedef list_c<int,1,2,3,5,8,13,21> something;
BOOST_STATIC_ASSERT(size<something>::type::value == 7);
typedef push_front< something,integral_c<int,1> >::type fibonacci;
BOOST_STATIC_ASSERT(size<fibonacci>::type::value == 8);
BOOST_STATIC_ASSERT((equal< fibonacci,list_c<int,1,1,2,3,5,8,13,21>,equal_to<_,_> >::type::value));

Notes

[1] The algorithm can be viewed as a notational shorcut to more verbose insert< Sequence,begin<Sequence>::type,T >::type, and is provided only if the sequence can meet the stated complexity requirements.

See also

Extensible Sequence, insert, front, pop_front, push_back


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Last edited September 11, 2002 4:27 am