How can I convert a std::string to int?

In C++11 there are some nice new convert functions from std::string to a number type.

So instead of

atoi( str.c_str() )

you can use

std::stoi( str )

where str is your number as std::string.

There are version for all flavours of numbers:
long stol(string), float stof(string), double stod(string),…
see http://en.cppreference.com/w/cpp/string/basic_string/stol