Compilare: user.cpp: In function ‘bool eval(const string&)’: user.cpp:74:19: warning: suggest parentheses around ‘&&’ within ‘||’ [-Wparentheses] num.top() = x&&!num.top() || !x&&num.top(); ^ user.cpp:83:1: warning: no return statement in function returning non-void [-Wreturn-type] } ^ user.cpp: In function ‘int main()’: user.cpp:117:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<(1<<nr);++i){ ^