# Sparse Vector

#### Description

The templated class `sparse_vector<T, A>` is the base container adaptor for sparse vectors. For a n-dimensional sparse vector and 0 <= i < n every non-zero element vi is mapped to the i-th element of the container.

#### Example

    int main () {
        using namespace boost::numeric::ublas;
        sparse_vector<double> v (3, 3);
        for (int i = 0; i < v.size (); ++ i)
            v (i) = i;
        std::cout << v << std::endl;
    }

#### Definition

Defined in the header vector_sparse.hpp.

#### Template parameters

Parameter | Description | Default
--- | --- | ---
`T` | The type of object stored in the sparse vector. |
`F` | Functor describing the storage organization. | `forward`
`A` | The type of the adapted array. | `map_array<std::size_t, T>`

#### Model of

Vector.

#### Type requirements

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

#### Public base classes

`vector_expression<sparse_vector<T, A> >`

#### Members

Member | Description
--- | ---
`sparse_vector ()` | Allocates a `sparse_vector` that holds zero elements.
`sparse_vector (size_type size, size_type non_zeros)` | Allocates a `sparse_vector` that holds at most `size` elements.
`sparse_vector (const sparse_vector &v)` | The copy constructor.
`template<class AE> sparse_vector (size_type non_zeros, const vector_expression<AE> &ae)` | The extended copy constructor.
`void resize (size_type size, size_type non_zeros)` | Reallocates a `sparse_vector` to hold at most `size` elements. The content of the `sparse_vector` is preserved.
`size_type size () const` | Returns the size of the `sparse_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.
`sparse_vector &operator = (const sparse_vector &v)` | The assignment operator.
`sparse_vector &assign_temporary (sparse_vector &v)` | Assigns a temporary. May change the sparse vector `v`.
`template<class AE> sparse_vector &operator = (const vector_expression<AE> &ae)` | The extended assignment operator.
`template<class AE> sparse_vector &assign (const vector_expression<AE> &ae)` | Assigns a vector expression to the sparse vector. Left and right hand side of the assignment should be independent.
`template<class AE> sparse_vector &operator += (const vector_expression<AE> &ae)` | A computed assignment operator. Adds the vector expression to the sparse vector.
`template<class AE> sparse_vector &plus_assign (const vector_expression<AE> &ae)` | Adds a vector expression to the sparse vector. Left and right hand side of the assignment should be independent.
`template<class AE> sparse_vector &operator -= (const vector_expression<AE> &ae)` | A computed assignment operator. Subtracts the vector expression from the sparse vector.
`template<class AE> sparse_vector &minus_assign (const vector_expression<AE> &ae)` | Subtracts a vector expression from the sparse vector. Left and right hand side of the assignment should be independent.
`template<class AT> sparse_vector &operator *= (const AT &at)` | A computed assignment operator. Multiplies the sparse vector with a scalar.
`template<class AT> sparse_vector &operator /= (const AT &at)` | A computed assignment operator. Divides the sparse vector through a scalar.
`void swap (sparse_vector &v)` | Swaps the contents of the sparse vectors.
`void insert (size_type i, const_reference t)` | Inserts the value `t` at the `i`-th element.
`void erase (size_type i)` | Erases the value at the `i`-th element.
`void clear ()` | Clears the sparse vector.
`const_iterator begin () const` | Returns a `const_iterator` pointing to the beginning of the `sparse_vector`.
`const_iterator end () const` | Returns a `const_iterator` pointing to the end of the `sparse_vector`.
`iterator begin ()` | Returns a `iterator` pointing to the beginning of the `sparse_vector`.
`iterator end ()` | Returns a `iterator` pointing to the end of the `sparse_vector`.
`const_reverse_iterator rbegin () const` | Returns a `const_reverse_iterator` pointing to the beginning of the reversed `sparse_vector`.
`const_reverse_iterator rend () const` | Returns a `const_reverse_iterator` pointing to the end of the reversed `sparse_vector`.
`reverse_iterator rbegin ()` | Returns a `reverse_iterator` pointing to the beginning of the reversed `sparse_vector`.
`reverse_iterator rend ()` | Returns a `reverse_iterator` pointing to the end of the reversed `sparse_vector`.

#### Interface

        // Array based sparse vector class
        template<class T, class A>
        class sparse_vector:
            public vector_expression<sparse_vector<T, A> > {
        public:
            typedef std::size_t size_type;
            typedef std::ptrdiff_t difference_type;
            typedef T value_type;
            typedef const T &const_reference;
            typedef T &reference;
            typedef const T *const_pointer;
            typedef T *pointer;
            typedef F functor_type;
            typedef A array_type;
            typedef const A const_array_type;
            typedef const sparse_vector<T, A> const_self_type;
            typedef sparse_vector<T, A> self_type;
            typedef const vector_const_reference<const_self_type> const_closure_type;
            typedef vector_reference<self_type> closure_type;
            typedef typename A::const_iterator const_iterator_type;
            typedef typename A::iterator iterator_type;
            typedef sparse_tag storage_category;

            // Construction and destruction
            sparse_vector ();
            sparse_vector (size_type size, size_type non_zeros = 0);
            sparse_vector (const sparse_vector &v);
            template<class AE>
            sparse_vector (const vector_expression<AE> &ae, size_type non_zeros = 0);

            // Accessors
            size_type size () const;
            size_type non_zeros () const;
            const_array_type &data () const;
            array_type &data ();

            // Resizing
            void resize (size_type size, size_type non_zeros = 0);

            // Element access
            const_reference operator () (size_type i) const;
            reference operator () (size_type i);

            const_reference operator [] (size_type i) const;
            reference operator [] (size_type i);

            // Assignment
            sparse_vector &operator = (const sparse_vector &v);
            sparse_vector &assign_temporary (sparse_vector &v);
            template<class AE>
            sparse_vector &operator = (const vector_expression<AE> &ae);
            template<class AE>
            sparse_vector &reset (const vector_expression<AE> &ae);
            template<class AE>
            sparse_vector &assign (const vector_expression<AE> &ae);
            template<class AE>
            sparse_vector &operator += (const vector_expression<AE> &ae);
            template<class AE>
            sparse_vector &plus_assign (const vector_expression<AE> &ae);
            template<class AE>
            sparse_vector &operator -= (const vector_expression<AE> &ae);
            template<class AE>
            sparse_vector &minus_assign (const vector_expression<AE> &ae);
            template<class AT>
            sparse_vector &operator *= (const AT &at);
            template<class AT>
            sparse_vector &operator /= (const AT &at);

            // Swapping
            void swap (sparse_vector &v);
            friend void swap (sparse_vector &v1, sparse_vector &v2);

            // Element insertion and erasure
            void insert (size_type i, const_reference t);
            void erase (size_type i);
            void clear ();

            class const_iterator;
            class iterator;

            // Element lookup
            const_iterator find (size_type i) const;
            iterator find (size_type i);
            const_iterator find_first (size_type i) const;
            iterator find_first (size_type i);
            const_iterator find_last (size_type i) const;
            iterator find_last (size_type i);

            // Iterators simply are pointers.

            class const_iterator:
                public container_const_reference<sparse_vector>,
                public bidirectional_iterator_base<const_iterator, value_type> {
            public:
                typedef sparse_bidirectional_iterator_tag iterator_category;
                typedef typename sparse_vector::difference_type difference_type;
                typedef typename sparse_vector::value_type value_type;
                typedef typename sparse_vector::const_reference reference;
                typedef typename sparse_vector::const_pointer pointer;

                // Construction and destruction
                const_iterator ();
                const_iterator (const sparse_vector &v, const const_iterator_type &it);
                const_iterator (const iterator &it);

                // Arithmetic
                const_iterator &operator ++ ();
                const_iterator &operator -- ();

                // Dereference
                reference operator * () const;

                // Index
                size_type index () const;

                // Assignment
                const_iterator &operator = (const const_iterator &it);

                // Comparison
                bool operator == (const const_iterator &it) const;
            };

            const_iterator begin () const;
            const_iterator end () const;

            class iterator:
                public container_reference<sparse_vector>,
                public bidirectional_iterator_base<iterator, value_type> {
            public:
                typedef sparse_bidirectional_iterator_tag iterator_category;
                typedef typename sparse_vector::difference_type difference_type;
                typedef typename sparse_vector::value_type value_type;
                typedef typename sparse_vector::reference reference;
                typedef typename sparse_vector::pointer pointer;

                // Construction and destruction
                iterator ();
                iterator (sparse_vector &v, const iterator_type &it);

                // Arithmetic
                iterator &operator ++ ();
                iterator &operator -- ();

                // Dereference
                reference operator * () const;

                // Index
                size_type index () const;

                // Assignment
                iterator &operator = (const iterator &it);

                // Comparison
                bool operator == (const iterator &it) const;
            };

            iterator begin ();
            iterator end ();

            // Reverse iterator

            typedef reverse_iterator_base<const_iterator> const_reverse_iterator;

            const_reverse_iterator rbegin () const;
            const_reverse_iterator rend () const;

            typedef reverse_iterator_base<iterator> reverse_iterator;

            reverse_iterator rbegin ();
            reverse_iterator rend ();
        };

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: 8/3/2002