Eroare de compilare: user.cpp: In function ‘int main()’: user.cpp:20:55: error: no match for ‘operator==’ (operand types are ‘std::string {aka std::basic_string<char>}’ and ‘char’) if(!st.empty() && str[st.top()] == '(' && str == ')'){ ^ user.cpp:20:55: note: candidates are: In file included from /usr/include/c++/4.8/iosfwd:40:0, from /usr/include/c++/4.8/ios:38, from /usr/include/c++/4.8/istream:38, from /usr/include/c++/4.8/fstream:38, from user.cpp:1: /usr/include/c++/4.8/bits/postypes.h:216:5: note: template<class _StateT> bool std::operator==(const std::fpos<_StateT>&, const std::fpos<_StateT>&) operator==(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs) ^ /usr/include/c++/4.8/bits/postypes.h:216:5: note: template argument deduction/substitution failed: user.cpp:20:58: note: ‘std::string {aka std::basic_string<char>}’ is not derived from ‘const std::fpos<_StateT>’ if(!st.empty() && str[st.top()] == '(' && str == ')'){ ^ In file included from /usr/include/c++/4.8/bits/stl_algobase.h:64:0, from /usr/include/c++/4.8/bits/char_traits.h:39, from /usr/include/c++/4.8/ios:40, from /usr/include/c++/4.8/istream:38, from /usr/include/c++/4.8/fstream:38, from user.cpp:1: /usr/include/c++/4.8/bits/stl_pair.h:214:5: note: template<class _T1, class _T2> constexpr bool std::operator==(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&) operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) ^ /usr/include/c++/4.8/bits/stl_pair.h:214:5: note: template argument deduction/substitution failed: user.cpp:20:58: note: ‘std::string {aka std::basic_string<char>}’ is not derived from ‘const std::pair<_T1, _T2>’ if(!st.empty() && str[st.top()] == '(' && str == ')'){ ^ In file included from /usr/include/c++/4.8/bits/stl_algobase.h:67:0, from /usr/include/c++/4.8/bits/char_traits.h:39, from /usr/include/c++/4.8/ios:40, from /usr/include/c++/4.8/istream:38, from /usr/include/c++/4.8/fstream:38, from user.cpp:1: /usr/include/c++/4.8/bits/stl_iterator.h:291:5: note: template<class _Iterator> bool std::operator==(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&) operator==(const reverse_iterator<_Iterator>& __x, ^ /usr/include/c++/4.8/bits/stl_iterator.h:291:5: note: template argument deduction/substitution failed: user.cpp:20:58: note: ‘std::string {aka std::basic_string<char>}’ is not derived from ‘const std::reverse_iterator<_Iterator>’ if(!st.empty() && str[st.top()] == '(' && str == ')'){ ^ In file included from /usr/include/c++/4.8/bits/stl_algobase.h:67:0, from /usr/include/c++/4.8/bits/char_traits.h:39, from /usr/include/c++/4.8/ios:40, from /usr/include/c++/4.8/istream:38, from /usr/include/c++/4.8/fstream:38, from user.cpp:1: /usr/include/c++/4.8/bits/stl_iterator.h:341:5: note: template<class _IteratorL, class _IteratorR> bool std::operator==(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_IteratorR>&)