Why overloaded < operator doesn't work with std::map
Hi
I am trying to use a class as the key datatype of a std::map container.
Based on map requirements, here is how I define my class:
class X {
public:
X() {};
~X() {};
X(const X&other);
bool operator<(const X& rhs);
X& operator=(const X& other);
int n;
};
bool X::operator<(const X& rhs) {
return n < rhs.n;
}
X& X::operator =(const X &other) {
if (this != &other) {
n = other.n;
}
return *this;
}
X::X(const X &other) {
n = other.n;
};
int main()
{
std::map<X,bool> map1;
std::pair<X, bool> pair1;
X a;
a.n = 1;
pair1.first = a;
pair1.second = true;
map1.insert(pair1);
return 1;
}
Upon compiling the code (by either VC++7.0 or g++) I get errors.
I figured out that either I had to define operator< as a friend or use
a functor as a key_compare, something like:
std::map<X,bool, cmpX>
But I am curious to know why the above code doesn't work even though
operator< is defined and it's publicly accessible.
thanks in advance
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