对存储在双端队列中的类对象进行排序

Question

I am trying to store email addresses written in a file and sort them by hits in the file.

I am storing the email addresses and the number of hits in a class called emailAddress.

I am managing the members of that class in a Deque in another class called AddressManager.

The sort function I am trying to use is the sort from the algorithm library. Like this.

[emailAddress.released() returns the number of hits. addressQueue is my emailAddress Deque]

bool AddressManager::swapTest(const emailAddress& address1, const emailAddress& address2)
{
    cout<<"Comparing: "<<address1.released()<<" to "<<address2.released()<<endl;
    return address1.released()>address2.released();
}
void AddressManager::sortAddresses()
{

    sort(addressQueue.begin(),addressQueue.end(),
        swapTest);
}

When I compile I get this error:

1>c:\workspace\addressmanager.cpp(36): error C3867: 'AddressManager::swapTest': function call missing argument list; use '&AddressManager::swapTest' to create a pointer to member
1>c:\workspace\addressmanager.cpp(36): error C2780: 'void std::sort(_RanIt,_RanIt)' : expects 2 arguments - 3 provided
1>          c:\program files (x86)\microsoft visual studio 10.0\vc\include\algorithm(3639) : see declaration of 'std::sort'

Can I pass swapTest to sort, or does it need to be defined outside of AddressManager somehow? Or could someone suggest a way to implement my own sort in AddressManager and not use the library version at all?

Thanks, ANkh

Answer 1

Just define an

struct EmailSorter
{
  bool EmailSorter::operator ()(const emailAddress &a, const emailAddress &b) {
    return a.released()>b.released();
  }
};

EmailSorter es;

std::sort( v.begin() , v.end() , es );

and pass it to std::sort

Or make swapTest a static function and do

std::sort( v.begin() , v.end() , &AddressManager::swapTest );

Answer 2

Either make swapTest a static function, or use a lambda:

sort(addressQueue.begin(),addressQueue.end(),
     [](const emailAddress& address1, const emailAddress& address2)
       { return address1.released() > address2.released(); }
     );