View Compilation Error

0_0_36782191_14861.cpp:11:11: error: empty character constant
    if(ch==''||ch=='\n'||ch==EOF){
           ^
0_0_36782191_14861.cpp: In function 'int main()':
0_0_36782191_14861.cpp:13:23: error: invalid use of member (did you forget the '&' ?)
      printf("%c",s.top);
                       ^