(C++) Property map

Part of the Boost C++ library.

The classes in this library are:

Example

Here is an example comparing a std::map to a const_associative_property_map. The latter will always give an error when a value is not found, a std::map has to be checked beforehand.

include <map>

include <cassert>

include <string>

include <boost/property_map.hpp>


std::map<std::string,int> GetMap()
{
  
  std::map<std::string,int> m;
  m.insert(std::make_pair("One",1));
  m.insert(std::make_pair("Ten",10));
  m.insert(std::make_pair("Hundred",100));
  return m;
}
int main()
{
  //Create a std::map
  typedef std::map<std::string,int> MyMap;
  const MyMap m = GetMap();
  //Search all values in std::map
  {
    assert(m.find("One")!=m.end());
    const int myStdOne = m.find("One")->second;
    assert(myStdOne == 1);
    assert(m.find("Ten")!=m.end());
    const int myStdTen = m.find("Ten")->second;
    assert(myStdTen == 10);
    assert(m.find("Hundred")!=m.end());
    const int myStdHundred = m.find("Hundred")->second;
    assert(myStdHundred == 100);
  }
  
  //Typedef the Boost map 
  typedef boost::const_associative_property_map<MyMap> BoostMap;
  //Copy std::map to Boost map
  const BoostMap boostNames(m);
  //Search all values in Boost map
  {
    const int myBoostOne = boost::get(boostNames,"One");
    assert(myBoostOne == 1);
    const int myBoostTen = boost::get(boostNames,"Ten");
    assert(myBoostTen == 10);
    const int myBoostHundred = boost::get(boostNames,"Hundred");
    assert(myBoostHundred == 100);
  }
}

Questions

What is the difference between a std::map and a boost::associative_property_map ?

When a nonexisting key value is given (e.g. "khwgfruiwgp" in the example above), the boost::associative_property_map's internal asserts will find it. For the std::map you have to write these asserts yourself every time.

You cannot iterate through a boost::associative_property_map, where with a std::map you can.

Code links

External links

The Boost documentation: http://www.boost.org/libs/property_map/property_map.html

last edited (March 7, 2007) by bilderbikkel, Number of views: 1771, Current Rev: 8 (Diff)

[Edit this page] [Page history] [What links here] [Discuss this topic] [Printer Friendly]