Main.cc: In function ‘int main()’: Main.cc:8:10: error: no match for ‘operator==’ (operand types are ‘std::string’ {aka ‘std::__cxx11::basic_string’} and ‘int’) 8 | if(a==0){ | ~^~~ | | | | | int | std::string {aka std::__cxx11::basic_string} In file included from /usr/include/c++/9/regex:62, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110, from Main.cc:1: /usr/include/c++/9/bits/regex.h:1026:5: note: candidate: ‘template bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, const std::__cxx11::sub_match<_BiIter>&)’ 1026 | operator==(const sub_match<_BiIter>& __lhs, const sub_match<_BiIter>& __rhs) | ^~~~~~~~ /usr/include/c++/9/bits/regex.h:1026:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::__cxx11::sub_match<_BiIter>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/regex:62, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110, from Main.cc:1: /usr/include/c++/9/bits/regex.h:1099:5: note: candidate: ‘template bool std::__cxx11::operator==(std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const std::__cxx11::sub_match<_BiIter>&)’ 1099 | operator==(const __sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>& __lhs, | ^~~~~~~~ /usr/include/c++/9/bits/regex.h:1099:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: mismatched types ‘const std::__cxx11::sub_match<_BiIter>’ and ‘int’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/regex:62, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110, from Main.cc:1: /usr/include/c++/9/bits/regex.h:1173:5: note: candidate: ‘template bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, std::__cxx11::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&)’ 1173 | operator==(const sub_match<_Bi_iter>& __lhs, | ^~~~~~~~ /usr/include/c++/9/bits/regex.h:1173:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::__cxx11::sub_match<_BiIter>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/regex:62, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110, from Main.cc:1: /usr/include/c++/9/bits/regex.h:1247:5: note: candidate: ‘template bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type*, const std::__cxx11::sub_match<_BiIter>&)’ 1247 | operator==(typename iterator_traits<_Bi_iter>::value_type const* __lhs, | ^~~~~~~~ /usr/include/c++/9/bits/regex.h:1247:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: mismatched types ‘const std::__cxx11::sub_match<_BiIter>’ and ‘int’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/regex:62, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110, from Main.cc:1: /usr/include/c++/9/bits/regex.h:1321:5: note: candidate: ‘template bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type*)’ 1321 | operator==(const sub_match<_Bi_iter>& __lhs, | ^~~~~~~~ /usr/include/c++/9/bits/regex.h:1321:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::__cxx11::sub_match<_BiIter>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/regex:62, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110, from Main.cc:1: /usr/include/c++/9/bits/regex.h:1395:5: note: candidate: ‘template bool std::__cxx11::operator==(const typename std::iterator_traits<_Iter>::value_type&, const std::__cxx11::sub_match<_BiIter>&)’ 1395 | operator==(typename iterator_traits<_Bi_iter>::value_type const& __lhs, | ^~~~~~~~ /usr/include/c++/9/bits/regex.h:1395:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: mismatched types ‘const std::__cxx11::sub_match<_BiIter>’ and ‘int’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/regex:62, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110, from Main.cc:1: /usr/include/c++/9/bits/regex.h:1473:5: note: candidate: ‘template bool std::__cxx11::operator==(const std::__cxx11::sub_match<_BiIter>&, const typename std::iterator_traits<_Iter>::value_type&)’ 1473 | operator==(const sub_match<_Bi_iter>& __lhs, | ^~~~~~~~ /usr/include/c++/9/bits/regex.h:1473:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::__cxx11::sub_match<_BiIter>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/regex:62, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110, from Main.cc:1: /usr/include/c++/9/bits/regex.h:1991:5: note: candidate: ‘template bool std::__cxx11::operator==(const std::__cxx11::match_results<_BiIter, _Alloc>&, const std::__cxx11::match_results<_BiIter, _Alloc>&)’ 1991 | operator==(const match_results<_Bi_iter, _Alloc>& __m1, | ^~~~~~~~ /usr/include/c++/9/bits/regex.h:1991:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::__cxx11::match_results<_BiIter, _Alloc>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/iosfwd:40, from /usr/include/c++/9/ios:38, from /usr/include/c++/9/istream:38, from /usr/include/c++/9/sstream:38, from /usr/include/c++/9/complex:45, from /usr/include/c++/9/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54, from Main.cc:1: /usr/include/c++/9/bits/postypes.h:222:5: note: candidate: ‘template bool std::operator==(const std::fpos<_StateT>&, const std::fpos<_StateT>&)’ 222 | operator==(const fpos<_StateT>& __lhs, const fpos<_StateT>& __rhs) | ^~~~~~~~ /usr/include/c++/9/bits/postypes.h:222:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::fpos<_StateT>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/bits/stl_algobase.h:64, from /usr/include/c++/9/bits/char_traits.h:39, from /usr/include/c++/9/ios:40, from /usr/include/c++/9/istream:38, from /usr/include/c++/9/sstream:38, from /usr/include/c++/9/complex:45, from /usr/include/c++/9/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54, from Main.cc:1: /usr/include/c++/9/bits/stl_pair.h:448:5: note: candidate: ‘template constexpr bool std::operator==(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)’ 448 | operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y) | ^~~~~~~~ /usr/include/c++/9/bits/stl_pair.h:448:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::pair<_T1, _T2>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/bits/stl_algobase.h:67, from /usr/include/c++/9/bits/char_traits.h:39, from /usr/include/c++/9/ios:40, from /usr/include/c++/9/istream:38, from /usr/include/c++/9/sstream:38, from /usr/include/c++/9/complex:45, from /usr/include/c++/9/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54, from Main.cc:1: /usr/include/c++/9/bits/stl_iterator.h:325:5: note: candidate: ‘template bool std::operator==(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&)’ 325 | operator==(const reverse_iterator<_Iterator>& __x, | ^~~~~~~~ /usr/include/c++/9/bits/stl_iterator.h:325:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::reverse_iterator<_Iterator>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/bits/stl_algobase.h:67, from /usr/include/c++/9/bits/char_traits.h:39, from /usr/include/c++/9/ios:40, from /usr/include/c++/9/istream:38, from /usr/include/c++/9/sstream:38, from /usr/include/c++/9/complex:45, from /usr/include/c++/9/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54, from Main.cc:1: /usr/include/c++/9/bits/stl_iterator.h:363:5: note: candidate: ‘template bool std::operator==(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_IteratorR>&)’ 363 | operator==(const reverse_iterator<_IteratorL>& __x, | ^~~~~~~~ /usr/include/c++/9/bits/stl_iterator.h:363:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::reverse_iterator<_Iterator>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/bits/stl_algobase.h:67, from /usr/include/c++/9/bits/char_traits.h:39, from /usr/include/c++/9/ios:40, from /usr/include/c++/9/istream:38, from /usr/include/c++/9/sstream:38, from /usr/include/c++/9/complex:45, from /usr/include/c++/9/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54, from Main.cc:1: /usr/include/c++/9/bits/stl_iterator.h:1136:5: note: candidate: ‘template bool std::operator==(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorR>&)’ 1136 | operator==(const move_iterator<_IteratorL>& __x, | ^~~~~~~~ /usr/include/c++/9/bits/stl_iterator.h:1136:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::move_iterator<_IteratorL>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/bits/stl_algobase.h:67, from /usr/include/c++/9/bits/char_traits.h:39, from /usr/include/c++/9/ios:40, from /usr/include/c++/9/istream:38, from /usr/include/c++/9/sstream:38, from /usr/include/c++/9/complex:45, from /usr/include/c++/9/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54, from Main.cc:1: /usr/include/c++/9/bits/stl_iterator.h:1142:5: note: candidate: ‘template bool std::operator==(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorL>&)’ 1142 | operator==(const move_iterator<_Iterator>& __x, | ^~~~~~~~ /usr/include/c++/9/bits/stl_iterator.h:1142:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::move_iterator<_IteratorL>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/string:41, from /usr/include/c++/9/bits/locale_classes.h:40, from /usr/include/c++/9/bits/ios_base.h:41, from /usr/include/c++/9/ios:42, from /usr/include/c++/9/istream:38, from /usr/include/c++/9/sstream:38, from /usr/include/c++/9/complex:45, from /usr/include/c++/9/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54, from Main.cc:1: /usr/include/c++/9/bits/allocator.h:167:5: note: candidate: ‘template bool std::operator==(const std::allocator<_CharT>&, const std::allocator<_T2>&)’ 167 | operator==(const allocator<_T1>&, const allocator<_T2>&) | ^~~~~~~~ /usr/include/c++/9/bits/allocator.h:167:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::allocator<_CharT>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/string:55, from /usr/include/c++/9/bits/locale_classes.h:40, from /usr/include/c++/9/bits/ios_base.h:41, from /usr/include/c++/9/ios:42, from /usr/include/c++/9/istream:38, from /usr/include/c++/9/sstream:38, from /usr/include/c++/9/complex:45, from /usr/include/c++/9/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54, from Main.cc:1: /usr/include/c++/9/bits/basic_string.h:6144:5: note: candidate: ‘template bool std::operator==(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&, const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)’ 6144 | operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs, | ^~~~~~~~ /usr/include/c++/9/bits/basic_string.h:6144:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: mismatched types ‘const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>’ and ‘int’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/string:55, from /usr/include/c++/9/bits/locale_classes.h:40, from /usr/include/c++/9/bits/ios_base.h:41, from /usr/include/c++/9/ios:42, from /usr/include/c++/9/istream:38, from /usr/include/c++/9/sstream:38, from /usr/include/c++/9/complex:45, from /usr/include/c++/9/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54, from Main.cc:1: /usr/include/c++/9/bits/basic_string.h:6152:5: note: candidate: ‘template typename __gnu_cxx::__enable_if::__value, bool>::__type std::operator==(const std::__cxx11::basic_string<_CharT>&, const std::__cxx11::basic_string<_CharT>&)’ 6152 | operator==(const basic_string<_CharT>& __lhs, | ^~~~~~~~ /usr/include/c++/9/bits/basic_string.h:6152:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: mismatched types ‘const std::__cxx11::basic_string<_CharT>’ and ‘int’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/string:55, from /usr/include/c++/9/bits/locale_classes.h:40, from /usr/include/c++/9/bits/ios_base.h:41, from /usr/include/c++/9/ios:42, from /usr/include/c++/9/istream:38, from /usr/include/c++/9/sstream:38, from /usr/include/c++/9/complex:45, from /usr/include/c++/9/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54, from Main.cc:1: /usr/include/c++/9/bits/basic_string.h:6166:5: note: candidate: ‘template bool std::operator==(const _CharT*, const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)’ 6166 | operator==(const _CharT* __lhs, | ^~~~~~~~ /usr/include/c++/9/bits/basic_string.h:6166:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: mismatched types ‘const _CharT*’ and ‘std::__cxx11::basic_string’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/string:55, from /usr/include/c++/9/bits/locale_classes.h:40, from /usr/include/c++/9/bits/ios_base.h:41, from /usr/include/c++/9/ios:42, from /usr/include/c++/9/istream:38, from /usr/include/c++/9/sstream:38, from /usr/include/c++/9/complex:45, from /usr/include/c++/9/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54, from Main.cc:1: /usr/include/c++/9/bits/basic_string.h:6178:5: note: candidate: ‘template bool std::operator==(const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*)’ 6178 | operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs, | ^~~~~~~~ /usr/include/c++/9/bits/basic_string.h:6178:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: mismatched types ‘const _CharT*’ and ‘int’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/bits/ios_base.h:46, from /usr/include/c++/9/ios:42, from /usr/include/c++/9/istream:38, from /usr/include/c++/9/sstream:38, from /usr/include/c++/9/complex:45, from /usr/include/c++/9/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54, from Main.cc:1: /usr/include/c++/9/system_error:292:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_code&)’ 292 | operator==(const error_code& __lhs, const error_code& __rhs) noexcept | ^~~~~~~~ /usr/include/c++/9/system_error:292:32: note: no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string’} to ‘const std::error_code&’ 292 | operator==(const error_code& __lhs, const error_code& __rhs) noexcept | ~~~~~~~~~~~~~~~~~~^~~~~ /usr/include/c++/9/system_error:297:3: note: candidate: ‘bool std::operator==(const std::error_code&, const std::error_condition&)’ 297 | operator==(const error_code& __lhs, const error_condition& __rhs) noexcept | ^~~~~~~~ /usr/include/c++/9/system_error:297:32: note: no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string’} to ‘const std::error_code&’ 297 | operator==(const error_code& __lhs, const error_condition& __rhs) noexcept | ~~~~~~~~~~~~~~~~~~^~~~~ /usr/include/c++/9/system_error:304:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_code&)’ 304 | operator==(const error_condition& __lhs, const error_code& __rhs) noexcept | ^~~~~~~~ /usr/include/c++/9/system_error:304:37: note: no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string’} to ‘const std::error_condition&’ 304 | operator==(const error_condition& __lhs, const error_code& __rhs) noexcept | ~~~~~~~~~~~~~~~~~~~~~~~^~~~~ /usr/include/c++/9/system_error:311:3: note: candidate: ‘bool std::operator==(const std::error_condition&, const std::error_condition&)’ 311 | operator==(const error_condition& __lhs, | ^~~~~~~~ /usr/include/c++/9/system_error:311:37: note: no known conversion for argument 1 from ‘std::string’ {aka ‘std::__cxx11::basic_string’} to ‘const std::error_condition&’ 311 | operator==(const error_condition& __lhs, | ~~~~~~~~~~~~~~~~~~~~~~~^~~~~ In file included from /usr/include/c++/9/bits/locale_facets.h:48, from /usr/include/c++/9/bits/basic_ios.h:37, from /usr/include/c++/9/ios:44, from /usr/include/c++/9/istream:38, from /usr/include/c++/9/sstream:38, from /usr/include/c++/9/complex:45, from /usr/include/c++/9/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54, from Main.cc:1: /usr/include/c++/9/bits/streambuf_iterator.h:208:5: note: candidate: ‘template bool std::operator==(const std::istreambuf_iterator<_CharT, _Traits>&, const std::istreambuf_iterator<_CharT, _Traits>&)’ 208 | operator==(const istreambuf_iterator<_CharT, _Traits>& __a, | ^~~~~~~~ /usr/include/c++/9/bits/streambuf_iterator.h:208:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::istreambuf_iterator<_CharT, _Traits>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54, from Main.cc:1: /usr/include/c++/9/complex:463:5: note: candidate: ‘template constexpr bool std::operator==(const std::complex<_Tp>&, const std::complex<_Tp>&)’ 463 | operator==(const complex<_Tp>& __x, const complex<_Tp>& __y) | ^~~~~~~~ /usr/include/c++/9/complex:463:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::complex<_Tp>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54, from Main.cc:1: /usr/include/c++/9/complex:468:5: note: candidate: ‘template constexpr bool std::operator==(const std::complex<_Tp>&, const _Tp&)’ 468 | operator==(const complex<_Tp>& __x, const _Tp& __y) | ^~~~~~~~ /usr/include/c++/9/complex:468:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::complex<_Tp>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54, from Main.cc:1: /usr/include/c++/9/complex:473:5: note: candidate: ‘template constexpr bool std::operator==(const _Tp&, const std::complex<_Tp>&)’ 473 | operator==(const _Tp& __x, const complex<_Tp>& __y) | ^~~~~~~~ /usr/include/c++/9/complex:473:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: mismatched types ‘const std::complex<_Tp>’ and ‘int’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/deque:67, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:68, from Main.cc:1: /usr/include/c++/9/bits/stl_deque.h:286:5: note: candidate: ‘template bool std::operator==(const std::_Deque_iterator<_Tp, _Ref, _Ptr>&, const std::_Deque_iterator<_Tp, _Ref, _Ptr>&)’ 286 | operator==(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x, | ^~~~~~~~ /usr/include/c++/9/bits/stl_deque.h:286:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::_Deque_iterator<_Tp, _Ref, _Ptr>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/deque:67, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:68, from Main.cc:1: /usr/include/c++/9/bits/stl_deque.h:293:5: note: candidate: ‘template bool std::operator==(const std::_Deque_iterator<_Tp, _Ref, _Ptr>&, const std::_Deque_iterator<_Tp, _RefR, _PtrR>&)’ 293 | operator==(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x, | ^~~~~~~~ /usr/include/c++/9/bits/stl_deque.h:293:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::_Deque_iterator<_Tp, _Ref, _Ptr>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/deque:67, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:68, from Main.cc:1: /usr/include/c++/9/bits/stl_deque.h:2312:5: note: candidate: ‘template bool std::operator==(const std::deque<_Tp, _Alloc>&, const std::deque<_Tp, _Alloc>&)’ 2312 | operator==(const deque<_Tp, _Alloc>& __x, | ^~~~~~~~ /usr/include/c++/9/bits/stl_deque.h:2312:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::deque<_Tp, _Alloc>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/tuple:39, from /usr/include/c++/9/functional:54, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:71, from Main.cc:1: /usr/include/c++/9/array:252:5: note: candidate: ‘template bool std::operator==(const std::array<_Tp, _Nm>&, const std::array<_Tp, _Nm>&)’ 252 | operator==(const array<_Tp, _Nm>& __one, const array<_Tp, _Nm>& __two) | ^~~~~~~~ /usr/include/c++/9/array:252:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::array<_Tp, _Nm>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/functional:54, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:71, from Main.cc:1: /usr/include/c++/9/tuple:1419:5: note: candidate: ‘template constexpr bool std::operator==(const std::tuple<_Tps ...>&, const std::tuple<_Elements ...>&)’ 1419 | operator==(const tuple<_TElements...>& __t, | ^~~~~~~~ /usr/include/c++/9/tuple:1419:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::tuple<_Tps ...>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/functional:59, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:71, from Main.cc:1: /usr/include/c++/9/bits/std_function.h:746:5: note: candidate: ‘template bool std::operator==(const std::function<_Res(_ArgTypes ...)>&, std::nullptr_t)’ 746 | operator==(const function<_Res(_Args...)>& __f, nullptr_t) noexcept | ^~~~~~~~ /usr/include/c++/9/bits/std_function.h:746:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::function<_Res(_ArgTypes ...)>’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/functional:59, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:71, from Main.cc:1: /usr/include/c++/9/bits/std_function.h:752:5: note: candidate: ‘template bool std::operator==(std::nullptr_t, const std::function<_Res(_ArgTypes ...)>&)’ 752 | operator==(nullptr_t, const function<_Res(_Args...)>& __f) noexcept | ^~~~~~~~ /usr/include/c++/9/bits/std_function.h:752:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: mismatched types ‘const std::function<_Res(_ArgTypes ...)>’ and ‘int’ 8 | if(a==0){ | ^ In file included from /usr/include/c++/9/bits/locale_conv.h:41, from /usr/include/c++/9/locale:43, from /usr/include/c++/9/iomanip:43, from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:72, from Main.cc:1: /usr/include/c++/9/bits/unique_ptr.h:715:5: note: candidate: ‘template bool std::operator==(const std::unique_ptr<_Tp, _Dp>&, const std::unique_ptr<_Up, _Ep>&)’ 715 | operator==(const unique_ptr<_Tp, _Dp>& __x, | ^~~~~~~~ /usr/include/c++/9/bits/unique_ptr.h:715:5: note: template argument deduction/substitution failed: Main.cc:8:12: note: ‘std::string’ {aka ‘std::__cxx11::basic_string’} is not derived from ‘const std::unique_ptr<_Tp, _Dp>’