Language: C++

#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
 
int main() {
  string b;
  cin >> b;
  if(b == 'A') cout << 'T';
  if(b == 'C') cout << 'G';
  if(b == 'G') cout << 'C';
  if(b == 'T') cout << 'A';
}


Compiler output:
a.cc: In function 'int main()':
a.cc:8:8: error: no match for 'operator==' (operand types are 'std::string' {aka 'std::__cxx11::basic_string<char>'} and 'char')
    8 |   if(b == 'A') cout << 'T';
      |      ~ ^~ ~~~
      |      |    |
      |      |    char
      |      std::string {aka std::__cxx11::basic_string<char>}
In file included from /usr/include/c++/14/regex:68,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:181,
                 from a.cc:2:
/usr/include/c++/14/bits/regex.h:1103:5: note: candidate: 'template<class _BiIter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const sub_match<_BiIter>&)'
 1103 |     operator==(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs)
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1103:5: note:   template argument deduction/substitution failed:
a.cc:8:11: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
    8 |   if(b == 'A') cout << 'T';
      |           ^~~
/usr/include/c++/14/bits/regex.h:1199:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const sub_match<_BiIter>&)'
 1199 |     operator==(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1199:5: note:   template argument deduction/substitution failed:
a.cc:8:11: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'char'
    8 |   if(b == 'A') cout << 'T';
      |           ^~~
/usr/include/c++/14/bits/regex.h:1274:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::__cxx11::operator==(const sub_match<_BiIter>&, __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)'
 1274 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1274:5: note:   template argument deduction/substitution failed:
a.cc:8:11: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
    8 |   if(b == 'A') cout << 'T';
      |           ^~~
/usr/include/c++/14/bits/regex.h:1366:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type*, const sub_match<_BiIter>&)'
 1366 |     operator==(typename iterator_traits<_Bi_iter>::value_type const* __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1366:5: note:   template argument deduction/substitution failed:
a.cc:8:11: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'char'
    8 |   if(b == 'A') cout << 'T';
      |           ^~~
/usr/include/c++/14/bits/regex.h:1441:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)'
 1441 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1441:5: note:   template argument deduction/substitution failed:
a.cc:8:11: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
    8 |   if(b == 'A') cout << 'T';
      |           ^~~
/usr/include/c++/14/bits/regex.h:1534:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type&, const sub_match<_BiIter>&)'
 1534 |     operator==(typename iterator_traits<_Bi_iter>::value_type const& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1534:5: note:   template argument deduction/substitution failed:
a.cc:8:11: note:   mismatched types 'const std::__cxx11::sub_match<_BiIter>' and 'char'
    8 |   if(b == 'A') cout << 'T';
      |           ^~~
/usr/include/c++/14/bits/regex.h:1613:5: note: candidate: 'template<class _Bi_iter> bool std::__cxx11::operator==(const sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)'
 1613 |     operator==(const sub_match<_Bi_iter>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:1613:5: note:   template argument deduction/substitution failed:
a.cc:8:11: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__cxx11::sub_match<_BiIter>'
    8 |   if(b == 'A') cout << 'T';
      |           ^~~
/usr/include/c++/14/bits/regex.h:2186:5: note: candidate: 'template<class _Bi_iter, class _Alloc> bool std::__cxx11::operator==(const match_results<_BiIter, _Alloc>&, const match_results<_BiIter, _Alloc>&)'
 2186 |     operator==(const match_results<_Bi_iter, _Alloc>& __m1,
      |     ^~~~~~~~
/usr/include/c++/14/bits/regex.h:2186:5: note:   template argument deduction/substitution failed:
a.cc:8:11: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__cxx11::match_results<_BiIter, _Alloc>'
    8 |   if(b == 'A') cout << 'T';
      |           ^~~
In file included from /usr/include/c++/14/unordered_map:46,
                 from /usr/include/c++/14/functional:63,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:53:
/usr/include/c++/14/debug/unordered_map:855:5: note: candidate: 'template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> bool std::__debug::operator==(const unordered_map<_Key, _Tp, _Hash, _Pred, _Allocator>&, const unordered_map<_Key, _Tp, _Hash, _Pred, _Allocator>&)'
  855 |     operator==(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/debug/unordered_map:855:5: note:   template argument deduction/substitution failed:
a.cc:8:11: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__debug::unordered_map<_Key, _Tp, _Hash, _Pred, _Allocator>'
    8 |   if(b == 'A') cout << 'T';
      |           ^~~
/usr/include/c++/14/debug/unordered_map:1572:5: note: candidate: 'template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> bool std::__debug::operator==(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Allocator>&, const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Allocator>&)'
 1572 |     operator==(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
      |     ^~~~~~~~
/usr/include/c++/14/debug/unordered_map:1572:5: note:   template argument deduction/substitution failed:
a.cc:8:11: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__debug::unordered_multimap<_Key, _Tp, _Hash, _Pred, _Allocator>'
    8 |   if(b == 'A') cout << 'T';
      |           ^~~
In file included from /usr/include/c++/14/vector:76,
                 from /usr/include/c++/14/functional:64:
/usr/include/c++/14/debug/vector:871:5: note: candidate: 'template<class _Tp, class _Alloc> bool std::__debug::operator==(const vector<_Tp, _Alloc>&, const vector<_Tp, _Alloc>&)'
  871 |     operator==(const vector<_Tp, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/debug/vector:871:5: note:   template argument deduction/substitution failed:
a.cc:8:11: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__debug::vector<_Tp, _Alloc>'
    8 |   if(b == 'A') cout << 'T';
      |           ^~~
In file included from /usr/include/c++/14/deque:77,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:139:
/usr/include/c++/14/debug/deque:672:5: note: candidate: 'template<class _Tp, class _Alloc> bool std::__debug::operator==(const deque<_Tp, _Allocator>&, const deque<_Tp, _Allocator>&)'
  672 |     operator==(const deque<_Tp, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/debug/deque:672:5: note:   template argument deduction/substitution failed:
a.cc:8:11: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__debug::deque<_Tp, _Allocator>'
    8 |   if(b == 'A') cout << 'T';
      |           ^~~
In file included from /usr/include/c++/14/list:69,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:150:
/usr/include/c++/14/debug/list:925:5: note: candidate: 'template<class _Tp, class _Alloc> bool std::__debug::operator==(const list<_Tp, _Allocator>&, const list<_Tp, _Allocator>&)'
  925 |     operator==(const list<_Tp, _Alloc>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/debug/list:925:5: note:   template argument deduction/substitution failed:
a.cc:8:11: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__debug::list<_Tp, _Allocator>'
    8 |   if(b == 'A') cout << 'T';
      |           ^~~
In file included from /usr/include/c++/14/debug/map:43,
                 from /usr/include/c++/14/map:69,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:152:
/usr/include/c++/14/debug/map.h:748:5: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Allocator> bool std::__debug::operator==(const map<_Key, _Tp, _Compare, _Allocator>&, const map<_Key, _Tp, _Compare, _Allocator>&)'
  748 |     operator==(const map<_Key, _Tp, _Compare, _Allocator>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/debug/map.h:748:5: note:   template argument deduction/substitution failed:
a.cc:8:11: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__debug::map<_Key, _Tp, _Compare, _Allocator>'
    8 |   if(b == 'A') cout << 'T';
      |           ^~~
In file included from /usr/include/c++/14/debug/map:44:
/usr/include/c++/14/debug/multimap.h:630:5: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Allocator> bool std::__debug::operator==(const multimap<_Key, _Tp, _Compare, _Allocator>&, const multimap<_Key, _Tp, _Compare, _Allocator>&)'
  630 |     operator==(const multimap<_Key, _Tp, _Compare, _Allocator>& __lhs,
      |     ^~~~~~~~
/usr/include/c++/14/debug/multimap.h:630:5: note:   template argument deduction/substitution failed:
a.cc:8:11: note:   'std::string' {aka 'std::__cxx11::basic_string<char>'} is not derived from 'const std::__debug::multimap<_Key, _Tp, _Compare, _Allocat