Compilare: main.cpp: In function 'void eval()': main.cpp:19:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(poz<str.size()) ~~~^~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:130:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<str.size(); i++) ~^~~~~~~~~~~