View Compilation Error

0_0_1367288_22595.cpp: In function `int main()':
0_0_1367288_22595.cpp:15: error: no match for 'operator==' in 'str == '(''
0_0_1367288_22595.cpp:17: error: no matching function for call to `std::stack<char, std::deque<char, std::allocator<char> > >::push(std::string&)'
GCC/bin/../lib/gcc/mingw32/3.4.2/../../../../include/c++/3.4.2/bits/stl_stack.h:191: note: candidates are: void std::stack<_Tp, _Sequence>::push(const typename _Sequence::value_type&) [with _Tp = char, _Sequence = std::deque<char, std::allocator<char> >]
0_0_1367288_22595.cpp:19: error: no match for 'operator==' in 'str == ')''
0_0_1367288_22595.cpp:23: error: no match for 'operator==' in 'str == 'B''