Compilare: main.cpp: In function 'int main()': main.cpp:45:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<strlen(s); i++) ~^~~~~~~~~~ main.cpp:60:52: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(strchr("0123456789",s[i])!=0 && i<strlen(s)) ~^~~~~~~~~~ main.cpp:65:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(s[i]=='+' || s[i]=='-' || i==strlen(s)) ~^~~~~~~~~~~