View Compilation Error

0_0_29889834_22169.cpp:17:20: error: empty character constant
             if(ch=='' || ch=='\n' || ch==EOF)
                    ^
0_0_29889834_22169.cpp: In function 'int main()':
0_0_29889834_22169.cpp:22:26: error: statement cannot resolve address of overloaded function
                     s.pop;
                          ^