push_front
template<
typename Sequence
, typename T
>
struct push_front
{
typedef unspecified type;
};
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.
#include "boost/mpl/push_front.hpp"
| Parameter | Requirement | Description |
|---|---|---|
Sequence | A model of Extensible Sequence | A sequence to handle the insert operation. |
T | A type | The element to be inserted. |
| 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 |
Amortized constant time [1].
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));
[1] The algorithm is 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.
Extensible Sequence, insert, front, pop_front, push_back