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

Expression semantics

Expression	Expression type	Precondition	Semantics	Postcondition
typedef push_front<Sequence,T>::type s;	A model of Extensible Sequence		Equivalent 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