Errors when creating set

Question

I would like to know why i am unable to create a set. I am getting the following error

Here is my codes.

Point.cpp My Point class

bool Point::operator<(const Point& p2)const {
return p21.length < p2.getScalarValue();
}

bool Point::operator>(const Point p2) {
bool result;
result = length > p2.getScalarValue();
return result;

}

and in my main.cpp

set<Point> s_p2;
Point tempp2;
s_p2.insert(tempp2);

After following your inputs, i have edited the codes and i have the following error

Point.cpp:56:46: error: passing ‘const Point’ as ‘this’ argument of ‘double Point::getScalarValue()’ discards qualifiers [-fpermissive]

Is this because i got two comparing statements ?

Answer 1

There is no std::set::insert overload that takes a bool as second paramater. You can insert like this:

s_p2.insert(tempp2);

Your operator< could be improved too, by making it a const method, taking a const reference parameter:

class Point {
  // as before
  bool operator<(const Point& p) const;
};  //                            ^ here, const method

bool Point::operator<(const Point& p2) const {
  return length < p2.length;
}

You could also choose to make it a non-member function:

bool operator<(const Point& lhs, const Point& rhs) {
  return lhs.getScalarValue() < rhs.getScalarValue();
}

This has the advantage of being completely symmetric to LHS and RHS. This matters if you have implicit conversions to Point or typed derived from Point.