# Vector Proxies

## Vector Range

#### Description

The templated class `vector_range<V>` allows addressing a range of a vector.

#### Example

    #include <boost/numeric/ublas/vector.hpp>

    #include <boost/numeric/ublas/io.hpp>

    int main () {

        using namespace boost::numeric::ublas;

        vector<double> v (3);

        vector_range<vector<double> > vr (v, range (0, 3));

        for (unsigned i = 0; i < vr.size (); ++ i)

            vr (i) = i;

        std::cout << vr << std::endl;

    }

#### Definition

Defined in the header vector_proxy.hpp.

#### Template parameters

Parameter | Description | Default
--- | --- | ---
`V` | The type of vector referenced. |

#### Model of

Vector Expression .

#### Type requirements

None, except for those imposed by the requirements of Vector Expression .

#### Public base classes

`vector_expression<vector_range<V> >`

#### Members

Member | Description
--- | ---
`vector_range (vector_type &data, const range &r)` | Constructs a sub vector.
`size_type start () const` | Returns the start of the sub vector.
`size_type size () const` | Returns the size of the sub vector.
`const_reference operator () (size_type i) const` | Returns the value of the `i`-th element.
`reference operator () (size_type i)` | Returns a reference of the `i`-th element.
`const_reference operator [] (size_type i) const` | Returns the value of the `i`-th element.
`reference operator [] (size_type i)` | Returns a reference of the `i`-th element.
`vector_range &operator = (const vector_range &vr)` | The assignment operator.
`vector_range &assign_temporary (vector_range &vr)` | Assigns a temporary. May change the vector range `vr` .
`template<class AE> vector_range &operator = (const vector_expression<AE> &ae)` | The extended assignment operator.
`template<class AE> vector_range &assign (const vector_expression<AE> &ae)` | Assigns a vector expression to the sub vector. Left and right hand side of the assignment should be independent.
`template<class AE> vector_range &operator += (const vector_expression<AE> &ae)` | A computed assignment operator. Adds the vector expression to the sub vector.
`template<class AE> vector_range &plus_assign (const vector_expression<AE> &ae)` | Adds a vector expression to the sub vector. Left and right hand side of the assignment should be independent.
`template<class AE> vector_range &operator -= (const vector_expression<AE> &ae)` | A computed assignment operator. Subtracts the vector expression from the sub vector.
`template<class AE> vector_range &minus_assign (const vector_expression<AE> &ae)` | Subtracts a vector expression from the sub vector. Left and right hand side of the assignment should be independent.
`template<class AT> vector_range &operator *= (const AT &at)` | A computed assignment operator. Multiplies the sub vector with a scalar.
`template<class AT> vector_range &operator /= (const AT &at)` | A computed assignment operator. Divides the sub vector through a scalar.
`void swap (vector_range &vr)` | Swaps the contents of the sub vectors.
`const_iterator begin () const` | Returns a `const_iterator` pointing to the beginning of the `vector_range`.
`const_iterator end () const` | Returns a `const_iterator` pointing to the end of the `vector_range`.
`iterator begin ()` | Returns a `iterator` pointing to the beginning of the `vector_range`.
`iterator end ()` | Returns a `iterator` pointing to the end of the `vector_range`.
`const_reverse_iterator rbegin () const` | Returns a `const_reverse_iterator` pointing to the beginning of the reversed `vector_range`.
`const_reverse_iterator rend () const` | Returns a `const_reverse_iterator` pointing to the end of the reversed `vector_range`.
`reverse_iterator rbegin ()` | Returns a `reverse_iterator` pointing to the beginning of the reversed `vector_range`.
`reverse_iterator rend ()` | Returns a `reverse_iterator` pointing to the end of the reversed `vector_range`.

### Projections

#### Prototypes

    template<class V>

        vector_range<V> project (V &data, const range &r);

        template<class V>

        const vector_range<const V> project (const V &data, const range &r);

        template<class V>

        vector_range<V> project (const vector_range<V> &data, const range &r);

#### Description

The free `project` functions support the construction of vector ranges.

#### Definition

Defined in the header vector_proxy.hpp.

#### Type requirements

- `V` is a model of Vector Expression .

#### Preconditions

- `r.start () + r.size () <= data.size ()`

#### Complexity

Linear depending from the size of the range.

#### Examples

    #include <boost/numeric/ublas/vector.hpp>

    #include <boost/numeric/ublas/io.hpp>

    int main () {

        using namespace boost::numeric::ublas;

        vector<double> v (3);

        for (int i = 0; i < 3; ++ i)

            project (v, range (0, 3)) (i) = i;

        std::cout << project (v, range (0, 3)) << std::endl;

    }

## Vector Slice

#### Description

The templated class `vector_slice<V>` allows addressing a slice of a vector.

#### Example

    #include <boost/numeric/ublas/vector.hpp>

    #include <boost/numeric/ublas/io.hpp>

    int main () {

        using namespace boost::numeric::ublas;

        vector<double> v (3);

        vector_slice<vector<double> > vs (v, slice (0, 1, 3));

        for (unsigned i = 0; i < vs.size (); ++ i)

            vs (i) = i;

        std::cout << vs << std::endl;

    }

#### Definition

Defined in the header vector_proxy.hpp.

#### Template parameters

Parameter | Description | Default
--- | --- | ---
`V` | The type of vector referenced. |

#### Model of

Vector Expression .

#### Type requirements

None, except for those imposed by the requirements of Vector Expression .

#### Public base classes

`vector_expression<vector_slice<V> >`

#### Members

Member | Description
--- | ---
`vector_slice (vector_type &data, const slice &s)` | Constructs a sub vector.
`size_type size () const` | Returns the size of the sub vector.
`const_reference operator () (size_type i) const` | Returns the value of the `i`-th element.
`reference operator () (size_type i)` | Returns a reference of the `i`-th element.
`const_reference operator [] (size_type i) const` | Returns the value of the `i`-th element.
`reference operator [] (size_type i)` | Returns a reference of the `i`-th element.
`vector_slice &operator = (const vector_slice &vs)` | The assignment operator.
`vector_slice &assign_temporary (vector_slice &vs)` | Assigns a temporary. May change the vector slice `vs` .
`template<class AE> vector_slice &operator = (const vector_expression<AE> &ae)` | The extended assignment operator.
`template<class AE> vector_slice &assign (const vector_expression<AE> &ae)` | Assigns a vector expression to the sub vector. Left and right hand side of the assignment should be independent.
`template<class AE> vector_slice &operator += (const vector_expression<AE> &ae)` | A computed assignment operator. Adds the vector expression to the sub vector.
`template<class AE> vector_slice &plus_assign (const vector_expression<AE> &ae)` | Adds a vector expression to the sub vector. Left and right hand side of the assignment should be independent.
`template<class AE> vector_slice &operator -= (const vector_expression<AE> &ae)` | A computed assignment operator. Subtracts the vector expression from the sub vector.
`template<class AE> vector_slice &minus_assign (const vector_expression<AE> &ae)` | Subtracts a vector expression from the sub vector. Left and right hand side of the assignment should be independent.
`template<class AT> vector_slice &operator *= (const AT &at)` | A computed assignment operator. Multiplies the sub vector with a scalar.
`template<class AT> vector_slice &operator /= (const AT &at)` | A computed assignment operator. Divides the sub vector through a scalar.
`void swap (vector_slice &vs)` | Swaps the contents of the sub vectors.
`const_iterator begin () const` | Returns a `const_iterator` pointing to the beginning of the `vector_slice`.
`const_iterator end () const` | Returns a `const_iterator` pointing to the end of the `vector_slice`.
`iterator begin ()` | Returns a `iterator` pointing to the beginning of the `vector_slice`.
`iterator end ()` | Returns a `iterator` pointing to the end of the `vector_slice`.
`const_reverse_iterator rbegin () const` | Returns a `const_reverse_iterator` pointing to the beginning of the reversed `vector_slice`.
`const_reverse_iterator rend () const` | Returns a `const_reverse_iterator` pointing to the end of the reversed `vector_slice`.
`reverse_iterator rbegin ()` | Returns a `reverse_iterator` pointing to the beginning of the reversed `vector_slice`.
`reverse_iterator rend ()` | Returns a `reverse_iterator` pointing to the end of the reversed `vector_slice`.

### Projections

#### Prototypes

    template<class V>

        vector_slice<V> project (const vector_slice<V> &data, const range &r);

        template<class V>

        vector_slice<V> project (V &data, const slice &s);

        template<class V>

        const vector_slice<const V> project (const V &data, const slice &s);

        template<class V>

        vector_slice<V> project (const vector_slice<V> &data, const slice &s);

#### Description

The free `project` functions support the construction of vector slices.

#### Definition

Defined in the header vector_proxy.hpp.

#### Type requirements

- `V` is a model of Vector Expression .

#### Preconditions

- `s.start () + s.stride () * s.size () <= data.size ()`

#### Complexity

Linear depending from the size of the slice.

#### Examples

    #include <boost/numeric/ublas/vector.hpp>

    #include <boost/numeric/ublas/io.hpp>

    int main () {

        using namespace boost::numeric::ublas;

        vector<double> v (3);

        for (int i = 0; i < 3; ++ i)

            project (v, slice (0, 1, 3)) (i) = i;

        std::cout << project (v, slice (0, 1, 3)) << std::endl;

    }

Copyright (©) 2000-2002 Joerg Walter, Mathias Koch
Permission to copy, use, modify, sell and distribute this document is granted provided this copyright notice appears in all copies. This document is provided ``as is'' without express or implied warranty, and with no claim as to its suitability for any purpose.

Last revised: 1/15/2003