foo.cc: In constructor 'Day::Day(std::string)':
foo.cc:34:28: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   34 |                 while(index<s.length())
      |                       ~~~~~^~~~~~~~~~~

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