/in/foo.cc: In function 'bool isNumber(const std::string&)':
/in/foo.cc:29:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   29 |         for(; i<s.size(); ++i)if(!isdigit(s[i]))return false;
      |               ~^~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:90:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::__cxx11::basic_string<char> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   90 |         for(int i=0; i<rows[0].cell.size(); ++i) {
      |                      ~^~~~~~~~~~~~~~~~~~~~
/in/foo.cc:96:31: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::__cxx11::basic_string<char> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   96 |                 for(int i=0; i<r.cell.size(); ++i) {
      |                              ~^~~~~~~~~~~~~~