foo.cc: In function 'int main(int, char**)':
foo.cc:20:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   20 |         while (nIndex < strExpression.size())
      |                ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
foo.cc:38:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   38 |         while (nIndex < strExpression.size())
      |                ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

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