How to properly use a vector range constructor?

Question

I want to load all the lines from a text file into a vector by using its range constructor and then output them through cout:

<         


        

Answer 1

You have fallen victim to the Most Vexing Parse, where the compiler sees your declaration as a function strings returning a vector<string>, taking two arguments:

• an istream_iterator<string> called file
• an unnamed pointer to function taking no arguments and returning a istream_iterator<string>.

To eliminate the vexing parse, use an extra pair of parentheses around the first argument:

vector<string> strings((istream_iterator<string>(file)) , istream_iterator<string>());
//                     ^                              ^

or, alternatively in C++11, use curly braces for the strings constructor

vector<string> strings{istream_iterator<string>(file) , istream_iterator<string>()};
//                    ^                                                           ^

NOTE: Clang warns you about it through -Wvexing-parse (on by default).