Compilare: user.cpp: In function ‘Node* parse(std::string&)’: user.cpp:122:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < nline.size(); ++i) { ^ user.cpp: In function ‘int main()’: user.cpp:205:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < vars.size(); ++i) { ^ user.cpp: In function ‘bool eval(Node*)’: user.cpp:51:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.cpp: In function ‘int get_priority(std::string&)’: user.cpp:61:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ user.cpp: In function ‘int get_operator(std::string&)’: user.cpp:71:1: warning: control reaches end of non-void function [-Wreturn-type] } ^