/in/foo.cc: In function 'int main()':
/in/foo.cc:14:13: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  while (pos < str.length() && str[pos] == '0') ++pos;
         ~~~~^~~~~~~~~~~~~~
/in/foo.cc:16:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (i = pos; i < str.length(); ++i)
                ~~^~~~~~~~~~~~~~
/in/foo.cc:29:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (i = 0; i < str.length() - 1; ++i)
              ~~^~~~~~~~~~~~~~~~~~