(C++) boost::get

Function from the Boost C++ Library. Used for Property Maps.

Example

The example below compares the std::map::find method to a boost::get on an boost::associative_property_map.

The boost::get function is shorter and internally asserts that the keyvalue is present.

include <map>

include <cassert>

include <boost/property_map.hpp>


struct MyKey
{
  MyKey(const int& x) : mX(x) {}
  const int mX;
};
bool operator<(const MyKey& lhs, const MyKey& rhs)
{
  return lhs.mX < rhs.mX;
}
struct MyValue
{
  MyValue(const int& y) : mY(y) {}
  const int mY;
};
bool operator==(const MyValue& lhs, const MyValue& rhs)
{
  return lhs.mY == rhs.mY;
}

std::map<MyKey,MyValue> GetMap()
{
  
  std::map<MyKey,MyValue> m;
  m.insert(std::make_pair(MyKey(1),MyValue(1)));
  m.insert(std::make_pair(MyKey(2),MyValue(4)));
  m.insert(std::make_pair(MyKey(3),MyValue(9)));
  return m;
}
int main()
{
  //Create a std::map
  typedef std::map<MyKey,MyValue> MyMap;
  
  const MyMap m = GetMap();
  //Search a values in std::map
  {
    const MyKey myKey(2);
    assert(m.find(myKey)!=m.end());
    const MyValue myValue = m.find(myKey)->second;
    assert(myValue == MyValue(4));
  }
  
  //Typedef the Boost map 
  typedef boost::const_associative_property_map<MyMap> BoostMap;
  //Copy std::map to Boost map
  const BoostMap boostNames(m);
  //Search a value in Boost map
  {
    const MyValue myValue = boost::get(boostNames,MyKey(2));
    assert(myValue == MyValue(4));
  }
}

Code links

last edited (March 7, 2007) by bilderbikkel, Number of views: 1182, Current Rev: 4 (Diff)

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