overloading operator== comparison 2 class - c++

Question

i'm new in programming and i'm trying to search an element in a list of class and i did this:
string x;
cin >> x;
list<Person>::iterator findIter = std::find(ListPerson.begin(), ListPerson.end(), x);
but it seem like i must overload the operator== to work, i did this:
friend bool operator== (Person &P1, Person &P2);
bool operator== (Person& P1, Person& P2)
{
return (P1.Name == P2.Name);
}
but it doesn't work i got always this error : c2678 binary '==' no operator found which takes a left-hand operand of type Person.
Thank you for helping !

Answer 1

Have you tried declaring the parameters as constant references? A comparison operator does not need to have side-effects.
The following works for me, and prints yeah:
#include <iostream>
using namespace std;
struct P {
const int x;
P(int x) {
this->x = x;
}
};
bool operator== (const P & p1, const P &p2) {
return p1.x == p2.x;
}
int main()
{
P x(0), y(0), z(1);
if (x == y) {
cout << "yeah" << endl;
}
if (y == z) {
cout << "nope" << endl;
}
}
Of course you might need to declare the operator== as a friend function if you want to do a comparison over private instance variables.
class P {
int x;
public:
P(int x) {
this->x = x;
}
friend bool operator== (const P &p1, const P &p2);
};

Answer 2

Your friend bool operator== declaration should be inside the class declaration. Next, pass by const reference instead, as rvalues cannot bind to non-const references and also the std::find expects its compared-to element by const reference. So your operator== should be able to compare const references, and non-const ones will not do since they will discard const qualifiers. To fix, declare
friend bool operator==(const Person &P1, const Person &P2);
Live working example here.