C++ overloaded operator linked sorted list ADT

1
votes

I have been trying to overload the equal (==) and less than (<) operators for a linked sorted list. I am not sure if I understand exactly if what I am doing makes sense. I have a struct with a string variable for DestinationCity, of which these operators have to compare. I have used strcmp in an attempt to make it work. Here is the code:

bool sortedListClass::operator <(const flightRec& rhs) const{
    
    
    if (strcmp(flightRec.DestinationCity, rhs.DestinationCity) < 0)
    { // I'm not sure if flightRec.DestionationCity is what I should write.
        return true;
    }
    else
        return false;

}
bool sortedListClass::operator ==(const flightRec& rhs) const{
       if (strcmp(flightRec.DestinationCity, rhs.DestinationCity) == 0)
    {
        return true;
    }
    else
        return false;
}

Here are the error messages.

sortedListClass.cpp: In member function ‘bool sortedListClass::operator<(const flightRec&) const’: sortedListClass.cpp:185:25: error: expected primary-expression before ‘.’ token

sortedListClass.cpp: In member function ‘bool sortedListClass::operator==(const flightRec&) const’: sortedListClass.cpp:194:28: error: expected primary-expression before ‘.’ token

3
c++operator-overloadingadt

3 Answers

3
votes

// I'm not sure if flightRec.DestionationCity is what I should write.

You shouldn't:-). If you want to define operator< on some class you do not do this in container class, but in the class which objects you want to compare. Here it would be flightRec.

bool flightRec::operator< (const flightRec& other) {
   // compare this and other
   if (strcmp(this->DestinationCity, other.DestinationCity))
   ...
}
0
votes

If you're still using std::string, don't compare with strcmp. == and < are both defined on string.

0
votes

If you want to leave the 'struct' without members, you can define the binary operator as a non-member:

bool operator <(const flightRec& lhs, const flightRec& rhs) 
{
   if (strcmp(lhs.DestinationCity, rhs.DestinationCity) < 0)
        return true;
    else
        return false;
}