Compilare: main.cpp: In function 'int eval(int, int)': main.cpp:29:8: warning: unused variable 'r' [-Wunused-variable] int r = 0; ^ main.cpp:61:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < op.size(); i++) { ~~^~~~~~~~~~~ main.cpp:23:6: warning: unused variable 'ln' [-Wunused-variable] int ln = -1; ^~ main.cpp: In function 'int main()': main.cpp:77:10: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (n<str.size()) { ~^~~~~~~~~~~ main.cpp:78:5: warning: operation on 'n' may be undefined [-Wsequence-point] v[++n] = str[n-1]; ^~~