Compilare: main.cpp: In function 'void convert(std::string, std::vector<polishExpressionElement>&, int&)': main.cpp:76:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 76 | for(int i = 0; i < expression.size(); i++){ | ~~^~~~~~~~~~~~~~~~~~~ main.cpp:82:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 82 | while(i < expression.size() && isNum(expression[i])){ | ~~^~~~~~~~~~~~~~~~~~~