Compilare: user.cpp: In function ‘int stringToInt(std::string)’: user.cpp:14:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<str.length();i++) ^ user.cpp: In function ‘int main()’: user.cpp:59:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=i+1;i<equation.size();i++) ^ user.cpp:75:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<leftSide.size();i++) ^ user.cpp:107:38: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<rightSide.size();i++) ^