[Solved] Does using the iterator member function “empty()” only work on certain vector types?

Question

empty() is not “an iterator member function”. You are not calling empty() on the iterator – you are dereferencing the iterator, and calling empty() on the vector element that the iterator refers to. It might be clearer if you replace iter->empty() with an equivalent form (*iter).empty()

In still other words,

auto iter = vec.begin();
iter->empty();

is equivalent to

vec[0].empty();

Here, iterators are not involved at all; hopefully, this would make the point extra clear.

Now, it so happens that std::string does have a member function empty(), while int of course does not (seeing as it’s not a class type and so can’t have any member functions). That’s why your code compiles with vector<string> but not vector<int>.

Accepted Answer

empty() is not “an iterator member function”. You are not calling empty() on the iterator – you are dereferencing the iterator, and calling empty() on the vector element that the iterator refers to. It might be clearer if you replace iter->empty() with an equivalent form (*iter).empty()

In still other words,

auto iter = vec.begin();
iter->empty();

is equivalent to

vec[0].empty();

Here, iterators are not involved at all; hopefully, this would make the point extra clear.

Now, it so happens that std::string does have a member function empty(), while int of course does not (seeing as it’s not a class type and so can’t have any member functions). That’s why your code compiles with vector<string> but not vector<int>.