Compilare: main.cpp: In function 'int main()': main.cpp:56:33: warning: array subscript has type 'char' [-Wchar-subscripts] while(optop>0 && pr[op[optop]]>=pr[s[i]]) ^ main.cpp:56:43: warning: array subscript has type 'char' [-Wchar-subscripts] while(optop>0 && pr[op[optop]]>=pr[s[i]]) ^ main.cpp: In function 'int calculate(int, int, char)': main.cpp:19:1: warning: control reaches end of non-void function [-Wreturn-type] } ^