prog.cpp: In function ‘int main()’:
prog.cpp:22:29: error: invalid initialization of non-const reference of type ‘std::string& {aka std::basic_string<char>&}’ from an rvalue of type ‘std::string {aka std::basic_string<char>}’
tokenize(get_input_string());
^
prog.cpp:10:8: error: in passing argument 1 of ‘tokens tokenize(std::string&)’
tokens tokenize(std::string& data)
^