/in/foo.cc: In function 'long long int evaluate(const std::string&, long long int)':
/in/foo.cc:49:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   49 |     for (int i = 0; i < expr.length(); i++) {
      |                     ~~^~~~~~~~~~~~~~~
/in/foo.cc:55:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   55 |             while (i < expr.length() && isdigit(expr[i])) {
      |                    ~~^~~~~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:125:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  125 |         for (int j = 0; j < test_values.size(); j++) {
      |                         ~~^~~~~~~~~~~~~~~~~~~~