Compilare: main.cpp: In function 'int evaluate(std::__cxx11::string)': main.cpp:40:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( int i = 0; i < e.size(); ++i) ~~^~~~~~~~~~ main.cpp:59:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i < e.size() and e[i] >= '0' and e[i] <= '9') ~~~^~~~~~~~~~ main.cpp: In function 'int calculateOperation(int, int, char)': main.cpp:33:1: warning: control reaches end of non-void function [-Wreturn-type] } ^