Compilare: main.cpp: In function 'std::__cxx11::string infixToPostfix(std::__cxx11::string)': main.cpp:47:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 5;i<a.size();i++) ~^~~~~~~~~ main.cpp: In function 'std::__cxx11::string lastInfixToPostfix(std::__cxx11::string)': main.cpp:66:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i<a.size();i++) ~^~~~~~~~~ main.cpp: In function 'long long int lastCalcFunction(char)': main.cpp:86:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i<a.size();i++) ~^~~~~~~~~ main.cpp: In function 'long long int calcFunction(char, long long int)': main.cpp:122:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i<a.size();i++) ~^~~~~~~~~ main.cpp: In function 'std::__cxx11::string firstFunctionInfixToPostfix(std::__cxx11::string)': main.cpp:157:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i<a.size();i++) ~^~~~~~~~~ main.cpp: In function 'void calculateMainFunctionVariables(std::__cxx11::string)': main.cpp:194:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0;i<a.size();i++) ~^~~~~~~~~