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| <Head> |
| <Title>Vector Property Map</Title> |
| <BODY BGCOLOR="#ffffff" LINK="#0000ee" TEXT="#000000" VLINK="#551a8b" |
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| <BR Clear> |
| |
| |
| <H2><A NAME="sec:vector-property-map"></A> |
| </h2> |
| <PRE> |
| template<typename T, typename IndexMap = identity_property_map> |
| class vector_property_map; |
| </PRE> |
| |
| <P> |
| This property map is used to efficiently store properties for a variable |
| number of elements. It's somewhere between <a |
| href="associative_property_map.html">associative_property_map</a> and |
| <a href="iterator_property_map.html">iterator_property_map</a>. The latter |
| is very fast, but requires that the number of stored elements is known |
| when creating property map. The former does not have this requirement, but |
| is slower, and requires stored elements to be comparable. |
| |
| <p> |
| The <tt>vector_property_map</tt> uses mapping from key to indices, |
| and allows to add new elements. It accoplishes this by storing values |
| in a vector, which is resized on demand. |
| |
| <p> |
| Note that <tt>vector_property_map</tt> does not provide reference/pointer |
| stability for stored values. |
| |
| <h3>Example</h3> |
| |
| <a href="../example/example3.cpp">example3.cpp</a>: |
| |
| <p> |
| <pre> |
| #include <boost/property_map/vector_property_map.hpp> |
| #include <string> |
| #include <iostream> |
| |
| int main() |
| { |
| boost::vector_property_map<std::string> m; |
| |
| // Assign string to '4'. |
| m[4] = "e"; |
| std::cout << "'" << m[4] << "'\n"; |
| |
| // Grab string from '10'. Since none is associated, |
| // "" will be returned. |
| std::cout << "'" << m[10] << "'\n"; |
| } |
| </pre> |
| |
| <H3>Where Defined</H3> |
| |
| <P> |
| <a href="../../../boost/property_map/vector_property_map.hpp"><TT>boost/property_map/vector_property_map.hpp</TT></a> |
| |
| <p> |
| <H3>Model Of</H3> |
| |
| <a href="./LvaluePropertyMap.html">Lvalue Property Map</a> |
| |
| <P> |
| |
| <H3>Template Parameters</H3> |
| |
| <P> |
| |
| <TABLE border> |
| <TR> |
| <th>Parameter</th><th>Description</th><th>Default</th> |
| </tr> |
| |
| |
| <TR> |
| <TD><TT>T</TT></TD> |
| <TD>The type of property value. Must be both <a |
| href="http://www.sgi.com/tech/stl/Assignable.html">Assignable</a> |
| and <a |
| href="http://www.sgi.com/tech/stl/DefaultConstructible.html">DefaultConstructible</a>. |
| </TD> |
| <TD> </td> |
| </tr> |
| |
| <TR> |
| <TD><TT>IndexMap</TT></TD> <TD>Must be a model of <a |
| href="./ReadablePropertyMap.html">Readable Property Map</a> |
| and the value type must be convertible to |
| <tt>std::vector<T>::size_type</tt>.</TD> |
| <TD><a href="identity_property_map.html">identity_property_map</a></TD> |
| </TR> |
| |
| </TABLE> |
| <P> |
| |
| <H3>Members</H3> |
| |
| <P> |
| In addition to the methods and functions required by <a |
| href="./LvaluePropertyMap.html">Lvalue Property Map</a>, this |
| class has the following members. |
| |
| <hr> |
| |
| <pre> |
| vector_property_map(const IndexMap& index = IndexMap()) |
| </pre> |
| Constructor which takes an index map. |
| |
| <hr> |
| |
| <pre> |
| vector_property_map(unsigned initial_size, const IndexMap& index = IndexMap()) |
| </pre> |
| This constructor version allows to specify maximum index of element |
| that will be stored. Correct number will improve performance, but semantic |
| is always the same. |
| |
| <hr> |
| |
| <pre> |
| vector_property_map(const vector_property_map&) |
| </pre> |
| Copy constructor. The copy will share the same data and changes |
| made to it will affect original property map. |
| |
| <hr> |
| |
| <pre> |
| vector_property_map& operator=(const vector_property_map&) |
| </pre> |
| Assignment operator. The semantic is the same as for copy constructor. |
| |
| <hr> |
| |
| <pre> |
| reference operator[](const key_type& v) const |
| </pre> |
| The operator bracket for property access. |
| |
| <hr> |
| |
| <pre> |
| std::vector<T>::iterator storage_begin() |
| std::vector<T>::iterator storage_end() |
| std::vector<T>::const_iterator storage_begin() |
| std::vector<T>::const_iterator storage_end() |
| </pre> |
| |
| <p>This group of methods gives access to begin and end iterators of the |
| underlying vector.</p> |
| |
| <p><b>Rationale:</b> The methods are handy, for example, when it's needed to |
| specify a single value for all elements in a freshly created property map. The |
| methods are not called simply "begin" and "end" since |
| conceptually, <tt>vector_property_map</tt> is unbounded map, and has no end |
| iterator. The direct access to the underlying method is not provided, since |
| it would decrease encapsulation and make future performance tuning dangerous. |
| |
| <p><b>Acknolegements:</b> Matthias Troyer suggested adding those functions. |
| |
| <hr> |
| |
| <pre> |
| void reserve(unsigned size) |
| </pre> |
| Reserve the space for storing elements with maximum index of 'size'. Unless |
| element with greater index is accesses, all accesses will be take O(1) time. |
| |
| |
| <hr> |
| |
| <h3>Non-Member functions</h3> |
| |
| <hr> |
| |
| <pre> |
| template<typename T, typename IndexMap> |
| vector_property_map<T, IndexMap> |
| make_vector_property_map(IndexMap index) |
| { |
| return vector_property_map<T, IndexMap>(index); |
| } |
| </pre> |
| A function for conveniently creating a vector property map. |
| |
| <br> |
| <HR> |
| <TABLE> |
| <TR valign=top> |
| <TD nowrap>Copyright © 2002</TD><TD> |
| <a HREF="http://www.boost.org/people/jeremy_siek.htm">Jeremy Siek</a>, |
| Indiana University (<A |
| HREF="mailto:jsiek@osl.iu.edu">jsiek@osl.iu.edu</A>)<br> |
| <A HREF="http://www.boost.org/people/liequan_lee.htm">Lie-Quan Lee</A>, Indiana University (<A HREF="mailto:llee1@osl.iu.edu">llee1@osl.iu.edu</A>)<br> |
| <A HREF="http://www.osl.iu.edu/~lums">Andrew Lumsdaine</A>, |
| Indiana University (<A |
| HREF="mailto:lums@osl.iu.edu">lums@osl.iu.edu</A>) |
| </TD></TR> |
| <tr> |
| <td nowrap>Copyright © 2003</td><td>Vladimir Prus</td> |
| </tr> |
| </TABLE> |
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