# Vector Proxies

## Vector Range

#### Description

The templated class `vector_range<V>` allows addressing a sub-range of a vector's element.

#### Example

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

If the specified range falls outside that of the index range of the vector, then the `vector_range` is not a well formed Vector Expression. That is, access to an element which is outside of index range of the vector is undefined.

#### 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`.

### Simple Projections

#### Description

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

#### Prototypes

        template<class V>
        vector_range<V> subrange (V &data,
           V::size_type start, V::size_type stop);
        template<class V>
        const vector_range<const V> subrange (const V &data,
           V::size_type start, V::size_type stop);

### Generic Projections

#### Description

The free `project` functions support the construction of vector ranges. Existing `matrix_range`'s can be composed with a further range. The resulting range is computed using this existing range's `compose` function.

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

#### Definition

Defined in the header vector_proxy.hpp.

#### Type requirements

- `V` is a model of Vector Expression .

#### Complexity

Linear depending from the size of the range.

#### Examples

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

If the specified slice falls outside that of the index range of the vector, then the `vector_slice` is not a well formed Vector Expression. That is, access to an element which is outside of index range of the vector is undefined.

#### 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`.

### Simple Projections

#### Description

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

#### Prototypes

        template<class V>
        vector_slice<V> subslice (V &data,
           V::size_type start, V::difference_type stride, V::size_type size);
        template<class V>
        const vector_slice<const V> subslice (const V &data,
           V::size_type start, V::difference_type stride, V::size_type size);

### Generic Projections

#### Description

The free `project` functions support the construction of vector slices. Existing `vector_slice`'s can be composed with a further range or slices. The resulting slice is computed using this existing slices's `compose` function.

#### Prototypes

        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 (vector_slice<V> &data, const range &r);
        template<class V>
        const vector_slice<V> project (const vector_slice<V> &data, const range &r);
        template<class V>
        vector_slice<V> project (vector_slice<V> &data, const slice &s);
        template<class V>
        const vector_slice<V> project (const vector_slice<V> &data, const slice &s);

#### Definition

Defined in the header vector_proxy.hpp.

#### Type requirements

- `V` is a model of Vector Expression .

#### Complexity

Linear depending from the size of the slice.

#### Examples

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