Compilare: user.cpp: In function ‘int main()’: user.cpp:38:3: warning: suggest explicit braces to avoid ambiguous ‘else’ [-Wparentheses] if(op==3) ^ user.cpp: In function ‘int op1(int)’: user.cpp:17:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.cpp: In function ‘int op2(int)’: user.cpp:25:1: warning: control reaches end of non-void function [-Wreturn-type] } ^