Why can't I assign one iterator to another in C++?

Question

I'm writing this function

vector<string> SplitIntoWords(const string& s) {
    vector<string> v_str = {};
    string::iterator str_b;
    str_b = begin(s);

    // TODO some action here

    return v_str;
}

and I need to declare an iterator which will be equal to begin of the string s, which is a parameter in my function.

The problem is with the line str_b = begin(s); - the code doesn't compile with it. Why so and how can I fix it?

Answer 1

Since s is const -qualified, begin(s) returns a string::const_iterator :

string::const_iterator str_b;
str_b = begin(s);

or better, let auto deduce str_b 's type from its initializer:

auto str_b = begin(s);

Answer 2

s is const object, so

begin(s)

returns string::const_iterator , you cannot assign string::const_iterator to string::iterator . You can fix it by

string::const_iterator str_b;