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# vector

### Description

`vector` is a variadic, random access, extensible sequence of types that supports constant-time insertion and removal of elements at both ends, and linear-time insertion and removal of elements in the middle. On compilers that support the `typeof` extension, `vector` is the simplest and in many cases the most efficient sequence.

### Header

Sequence form | Header
--- | ---
Variadic | `#include <boost/mpl/vector.hpp>`
Numbered | `#include <boost/mpl/vector/vector` n`.hpp>`

### Model of

- Variadic Sequence
- Random Access Sequence
- Extensible Sequence
- Back Extensible Sequence
- Front Extensible Sequence

### Expression semantics

In the following table, `v` is an instance of `vector`, `pos` and `last` are iterators into `v`, `r` is a Forward Sequence, `n` is an Integral Constant, and `x` and t1,t2,... tn are arbitrary types.

Expression | Semantics
--- | ---
    vector<t1,t2,... tn>
    vectorn<t1,t2,... tn>
| `vector` of elements t1,t2,... tn; see Variadic Sequence.
    vector<t1,t2,... tn>::type
    vectorn<t1,t2,... tn>::type
| Identical to `vector` n`<`t1,t2,... tn`>`; see Variadic Sequence.
`begin<v>::type` | An iterator pointing to the beginning of `v`; see Random Access Sequence.
`end<v>::type` | An iterator pointing to the end of `v`; see Random Access Sequence.
`size<v>::type` | The size of `v`; see Random Access Sequence.
`empty<v>::type` | A boolean Integral Constant `c` such that `c::value == true` if and only if the sequence is empty; see Random Access Sequence.
`front<v>::type` | The first element in `v`; see Random Access Sequence.
`back<v>::type` | The last element in `v`; see Random Access Sequence.
`at<v,n>::type` | The `n`th element from the beginning of `v`; see Random Access Sequence.
`insert<v,pos,x>::type` | A new `vector` of following elements: [`begin<v>::type`, `pos`), `x`, [`pos`, `end<v>::type`); see Extensible Sequence.
`insert_range<v,pos,r>::type` | A new `vector` of following elements: [`begin<v>::type`, `pos`), [`begin<r>::type`, `end<r>::type`) [`pos`, `end<v>::type`); see Extensible Sequence.
`erase<v,pos>::type` | A new `vector` of following elements: [`begin<v>::type`, `pos`), [`next<pos>::type`, `end<v>::type`); see Extensible Sequence.
`erase<v,pos,last>::type` | A new `vector` of following elements: [`begin<v>::type`, `pos`), [`last`, `end<v>::type`); see Extensible Sequence.
`clear<v>::type` | An empty `vector`; see Extensible Sequence.
`push_back<v,x>::type` | A new `vector` of following elements: [`begin<v>::type`, `end<v>::type`), `x`; see Back Extensible Sequence.
`pop_back<v>::type` | A new `vector` of following elements: [`begin<v>::type`, `prior< end<v>::type >::type`); see Back Extensible Sequence.
`push_front<v,x>::type` | A new `vector` of following elements: `x`, [`begin<v>::type`, `end<v>::type`); see Front Extensible Sequence.
`pop_front<v>::type` | A new `vector` of following elements: [`next< begin<v>::type >::type`, `end<v>::type`); see Front Extensible Sequence.

### Example

    typedef vector<float,double,long double> floats;
    typedef push_back<floats,int>::type types;

    BOOST_MPL_ASSERT(( is_same< at_c<types,3>::type, int > ));

### See also

Sequences, Variadic Sequence, Random Access Sequence, Extensible Sequence, vector_c, list