一行代码:
if((cin>>c)== -1)
引发的编译错误:
a.cpp: In function 'int main()':
a.cpp:21:24: error: no match for 'operator==' (operand types are 'std::basic_istream<char>' and 'int')
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ~~~~~~~~^~ ~~
| | |
| | int
| std::basic_istream<char>
a.cpp:21:24: note: candidate: 'operator==(int, int)' <built-in>
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ~~~~~~~~^~~~~
a.cpp:21:24: note: no known conversion for argument 1 from 'std::basic_istream<char>' to 'int'
In file included from /usr/include/c++/9/bits/stl_algobase.h:64,
from /usr/include/c++/9/bits/specfun.h:45,
from /usr/include/c++/9/cmath:1927,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:41,
from a.cpp:1:
/usr/include/c++/9/bits/stl_pair.h:448:5: note: candidate: 'template<class _T1, class _T2> 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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::pair<_T1, _T2>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/bits/stl_algobase.h:67,
from /usr/include/c++/9/bits/specfun.h:45,
from /usr/include/c++/9/cmath:1927,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:41,
from a.cpp:1:
/usr/include/c++/9/bits/stl_iterator.h:325:5: note: candidate: 'template<class _Iterator> constexpr 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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/bits/stl_algobase.h:67,
from /usr/include/c++/9/bits/specfun.h:45,
from /usr/include/c++/9/cmath:1927,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:41,
from a.cpp:1:
/usr/include/c++/9/bits/stl_iterator.h:363:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr 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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::reverse_iterator<_Iterator>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/bits/stl_algobase.h:67,
from /usr/include/c++/9/bits/specfun.h:45,
from /usr/include/c++/9/cmath:1927,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:41,
from a.cpp:1:
/usr/include/c++/9/bits/stl_iterator.h:1139:5: note: candidate: 'template<class _IteratorL, class _IteratorR> constexpr bool std::operator==(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorR>&)'
1139 | operator==(const move_iterator<_IteratorL>& __x,
| ^~~~~~~~
/usr/include/c++/9/bits/stl_iterator.h:1139:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::move_iterator<_IteratorL>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/bits/stl_algobase.h:67,
from /usr/include/c++/9/bits/specfun.h:45,
from /usr/include/c++/9/cmath:1927,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:41,
from a.cpp:1:
/usr/include/c++/9/bits/stl_iterator.h:1145:5: note: candidate: 'template<class _Iterator> constexpr bool std::operator==(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorL>&)'
1145 | operator==(const move_iterator<_Iterator>& __x,
| ^~~~~~~~
/usr/include/c++/9/bits/stl_iterator.h:1145:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::move_iterator<_IteratorL>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
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 a.cpp:1:
/usr/include/c++/9/bits/postypes.h:222:5: note: candidate: 'template<class _StateT> 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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::fpos<_StateT>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
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 a.cpp:1:
/usr/include/c++/9/bits/allocator.h:168:5: note: candidate: 'template<class _T1, class _T2> bool std::operator==(const std::allocator<_CharT>&, const std::allocator<_T2>&)'
168 | operator==(const allocator<_T1>&, const allocator<_T2>&)
| ^~~~~~~~
/usr/include/c++/9/bits/allocator.h:168:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::allocator<_CharT>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/bits/basic_string.h:48,
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 a.cpp:1:
/usr/include/c++/9/string_view:473:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator==(std::basic_string_view<_CharT, _Traits>, std::basic_string_view<_CharT, _Traits>)'
473 | operator==(basic_string_view<_CharT, _Traits> __x,
| ^~~~~~~~
/usr/include/c++/9/string_view:473:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/bits/basic_string.h:48,
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 a.cpp:1:
/usr/include/c++/9/string_view:479:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator==(std::basic_string_view<_CharT, _Traits>, std::__detail::__idt<std::basic_string_view<_CharT, _Traits> >)'
479 | operator==(basic_string_view<_CharT, _Traits> __x,
| ^~~~~~~~
/usr/include/c++/9/string_view:479:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'std::basic_string_view<_CharT, _Traits>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/bits/basic_string.h:48,
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 a.cpp:1:
/usr/include/c++/9/string_view:485:5: note: candidate: 'template<class _CharT, class _Traits> constexpr bool std::operator==(std::__detail::__idt<std::basic_string_view<_CharT, _Traits> >, std::basic_string_view<_CharT, _Traits>)'
485 | operator==(__detail::__idt<basic_string_view<_CharT, _Traits>> __x,
| ^~~~~~~~
/usr/include/c++/9/string_view:485:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: mismatched types 'std::basic_string_view<_CharT, _Traits>' and 'int'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
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 a.cpp:1:
/usr/include/c++/9/bits/basic_string.h:6141:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const std::basic_string<_CharT, _Traits, _Allocator>&, const std::basic_string<_CharT, _Traits, _Allocator>&)'
6141 | operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
| ^~~~~~~~
/usr/include/c++/9/bits/basic_string.h:6141:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::basic_string<_CharT, _Traits, _Allocator>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
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 a.cpp:1:
/usr/include/c++/9/bits/basic_string.h:6149:5: note: candidate: 'template<class _CharT> typename __gnu_cxx::__enable_if<std::__is_char<_Tp>::__value, bool>::__type std::operator==(const std::basic_string<_CharT>&, const std::basic_string<_CharT>&)'
6149 | operator==(const basic_string<_CharT>& __lhs,
| ^~~~~~~~
/usr/include/c++/9/bits/basic_string.h:6149:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::basic_string<_CharT>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
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 a.cpp:1:
/usr/include/c++/9/bits/basic_string.h:6163:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const _CharT*, const std::basic_string<_CharT, _Traits, _Allocator>&)'
6163 | operator==(const _CharT* __lhs,
| ^~~~~~~~
/usr/include/c++/9/bits/basic_string.h:6163:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: mismatched types 'const _CharT*' and 'std::basic_istream<char>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
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 a.cpp:1:
/usr/include/c++/9/bits/basic_string.h:6175:5: note: candidate: 'template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const std::basic_string<_CharT, _Traits, _Allocator>&, const _CharT*)'
6175 | operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
| ^~~~~~~~
/usr/include/c++/9/bits/basic_string.h:6175:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::basic_string<_CharT, _Traits, _Allocator>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
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 a.cpp: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::basic_istream<char>' 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::basic_istream<char>' 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::basic_istream<char>' 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::basic_istream<char>' 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 a.cpp:1:
/usr/include/c++/9/bits/streambuf_iterator.h:208:5: note: candidate: 'template<class _CharT, class _Traits> 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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::istreambuf_iterator<_CharT, _Traits>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/ccomplex:39,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
from a.cpp:1:
/usr/include/c++/9/complex:459:5: note: candidate: 'template<class _Tp> constexpr bool std::operator==(const std::complex<_Tp>&, const std::complex<_Tp>&)'
459 | operator==(const complex<_Tp>& __x, const complex<_Tp>& __y)
| ^~~~~~~~
/usr/include/c++/9/complex:459:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::complex<_Tp>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/ccomplex:39,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
from a.cpp:1:
/usr/include/c++/9/complex:464:5: note: candidate: 'template<class _Tp> constexpr bool std::operator==(const std::complex<_Tp>&, const _Tp&)'
464 | operator==(const complex<_Tp>& __x, const _Tp& __y)
| ^~~~~~~~
/usr/include/c++/9/complex:464:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::complex<_Tp>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/ccomplex:39,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:54,
from a.cpp:1:
/usr/include/c++/9/complex:469:5: note: candidate: 'template<class _Tp> constexpr bool std::operator==(const _Tp&, const std::complex<_Tp>&)'
469 | operator==(const _Tp& __x, const complex<_Tp>& __y)
| ^~~~~~~~
/usr/include/c++/9/complex:469:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: mismatched types 'const std::complex<_Tp>' and 'int'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/tuple:39,
from /usr/include/c++/9/functional:54,
from /usr/include/c++/9/pstl/glue_algorithm_defs.h:13,
from /usr/include/c++/9/algorithm:71,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:65,
from a.cpp:1:
/usr/include/c++/9/array:252:5: note: candidate: 'template<class _Tp, long unsigned int _Nm> 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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::array<_Tp, _Nm>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/functional:54,
from /usr/include/c++/9/pstl/glue_algorithm_defs.h:13,
from /usr/include/c++/9/algorithm:71,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:65,
from a.cpp:1:
/usr/include/c++/9/tuple:1419:5: note: candidate: 'template<class ... _TElements, class ... _UElements> 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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::tuple<_Tps ...>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/functional:59,
from /usr/include/c++/9/pstl/glue_algorithm_defs.h:13,
from /usr/include/c++/9/algorithm:71,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:65,
from a.cpp:1:
/usr/include/c++/9/bits/std_function.h:746:5: note: candidate: 'template<class _Res, class ... _Args> 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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::function<_Res(_ArgTypes ...)>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/functional:59,
from /usr/include/c++/9/pstl/glue_algorithm_defs.h:13,
from /usr/include/c++/9/algorithm:71,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:65,
from a.cpp:1:
/usr/include/c++/9/bits/std_function.h:752:5: note: candidate: 'template<class _Res, class ... _Args> 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:
a.cpp:21:28: note: mismatched types 'const std::function<_Res(_ArgTypes ...)>' and 'int'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/bits/node_handle.h:39,
from /usr/include/c++/9/bits/hashtable.h:37,
from /usr/include/c++/9/unordered_map:46,
from /usr/include/c++/9/functional:61,
from /usr/include/c++/9/pstl/glue_algorithm_defs.h:13,
from /usr/include/c++/9/algorithm:71,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:65,
from a.cpp:1:
/usr/include/c++/9/optional:983:5: note: candidate: 'template<class _Tp, class _Up> constexpr std::__optional_relop_t<decltype ((declval<_Tp>() == declval<_Up>()))> std::operator==(const std::optional<_Tp>&, const std::optional<_Up>&)'
983 | operator==(const optional<_Tp>& __lhs, const optional<_Up>& __rhs)
| ^~~~~~~~
/usr/include/c++/9/optional:983:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::optional<_Tp>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/bits/node_handle.h:39,
from /usr/include/c++/9/bits/hashtable.h:37,
from /usr/include/c++/9/unordered_map:46,
from /usr/include/c++/9/functional:61,
from /usr/include/c++/9/pstl/glue_algorithm_defs.h:13,
from /usr/include/c++/9/algorithm:71,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:65,
from a.cpp:1:
/usr/include/c++/9/optional:1034:5: note: candidate: 'template<class _Tp> constexpr bool std::operator==(const std::optional<_Tp>&, std::nullopt_t)'
1034 | operator==(const optional<_Tp>& __lhs, nullopt_t) noexcept
| ^~~~~~~~
/usr/include/c++/9/optional:1034:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::optional<_Tp>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/bits/node_handle.h:39,
from /usr/include/c++/9/bits/hashtable.h:37,
from /usr/include/c++/9/unordered_map:46,
from /usr/include/c++/9/functional:61,
from /usr/include/c++/9/pstl/glue_algorithm_defs.h:13,
from /usr/include/c++/9/algorithm:71,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:65,
from a.cpp:1:
/usr/include/c++/9/optional:1039:5: note: candidate: 'template<class _Tp> constexpr bool std::operator==(std::nullopt_t, const std::optional<_Tp>&)'
1039 | operator==(nullopt_t, const optional<_Tp>& __rhs) noexcept
| ^~~~~~~~
/usr/include/c++/9/optional:1039:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: mismatched types 'const std::optional<_Tp>' and 'int'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/bits/node_handle.h:39,
from /usr/include/c++/9/bits/hashtable.h:37,
from /usr/include/c++/9/unordered_map:46,
from /usr/include/c++/9/functional:61,
from /usr/include/c++/9/pstl/glue_algorithm_defs.h:13,
from /usr/include/c++/9/algorithm:71,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:65,
from a.cpp:1:
/usr/include/c++/9/optional:1095:5: note: candidate: 'template<class _Tp, class _Up> constexpr std::__optional_relop_t<decltype ((declval<_Tp>() == declval<_Up>()))> std::operator==(const std::optional<_Tp>&, const _Up&)'
1095 | operator==(const optional<_Tp>& __lhs, const _Up& __rhs)
| ^~~~~~~~
/usr/include/c++/9/optional:1095:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::optional<_Tp>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/bits/node_handle.h:39,
from /usr/include/c++/9/bits/hashtable.h:37,
from /usr/include/c++/9/unordered_map:46,
from /usr/include/c++/9/functional:61,
from /usr/include/c++/9/pstl/glue_algorithm_defs.h:13,
from /usr/include/c++/9/algorithm:71,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:65,
from a.cpp:1:
/usr/include/c++/9/optional:1101:5: note: candidate: 'template<class _Tp, class _Up> constexpr std::__optional_relop_t<decltype ((declval<_Up>() == declval<_Tp>()))> std::operator==(const _Up&, const std::optional<_Tp>&)'
1101 | operator==(const _Up& __lhs, const optional<_Tp>& __rhs)
| ^~~~~~~~
/usr/include/c++/9/optional:1101:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: mismatched types 'const std::optional<_Tp>' and 'int'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/unordered_map:47,
from /usr/include/c++/9/functional:61,
from /usr/include/c++/9/pstl/glue_algorithm_defs.h:13,
from /usr/include/c++/9/algorithm:71,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:65,
from a.cpp:1:
/usr/include/c++/9/bits/unordered_map.h:2091:5: note: candidate: 'template<class _Key1, class _Tp1, class _Hash1, class _Pred1, class _Alloc1> bool std::operator==(const std::unordered_map<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&, const std::unordered_map<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&)'
2091 | operator==(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
| ^~~~~~~~
/usr/include/c++/9/bits/unordered_map.h:2091:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::unordered_map<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/unordered_map:47,
from /usr/include/c++/9/functional:61,
from /usr/include/c++/9/pstl/glue_algorithm_defs.h:13,
from /usr/include/c++/9/algorithm:71,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:65,
from a.cpp:1:
/usr/include/c++/9/bits/unordered_map.h:2103:5: note: candidate: 'template<class _Key1, class _Tp1, class _Hash1, class _Pred1, class _Alloc1> bool std::operator==(const std::unordered_multimap<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&, const std::unordered_multimap<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>&)'
2103 | operator==(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
| ^~~~~~~~
/usr/include/c++/9/bits/unordered_map.h:2103:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::unordered_multimap<_Key1, _Tp1, _Hash1, _Pred1, _Alloc1>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/vector:67,
from /usr/include/c++/9/functional:62,
from /usr/include/c++/9/pstl/glue_algorithm_defs.h:13,
from /usr/include/c++/9/algorithm:71,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:65,
from a.cpp:1:
/usr/include/c++/9/bits/stl_vector.h:1888:5: note: candidate: 'template<class _Tp, class _Alloc> bool std::operator==(const std::vector<_Tp, _Alloc>&, const std::vector<_Tp, _Alloc>&)'
1888 | operator==(const vector<_Tp, _Alloc>& __x, const vector<_Tp, _Alloc>& __y)
| ^~~~~~~~
/usr/include/c++/9/bits/stl_vector.h:1888:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::vector<_Tp, _Alloc>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/deque:67,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:68,
from a.cpp:1:
/usr/include/c++/9/bits/stl_deque.h:286:5: note: candidate: 'template<class _Tp, class _Ref, class _Ptr> 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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::_Deque_iterator<_Tp, _Ref, _Ptr>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/deque:67,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:68,
from a.cpp:1:
/usr/include/c++/9/bits/stl_deque.h:293:5: note: candidate: 'template<class _Tp, class _RefL, class _PtrL, class _RefR, class _PtrR> 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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::_Deque_iterator<_Tp, _Ref, _Ptr>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/deque:67,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:68,
from a.cpp:1:
/usr/include/c++/9/bits/stl_deque.h:2312:5: note: candidate: 'template<class _Tp, class _Alloc> 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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::deque<_Tp, _Alloc>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
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 a.cpp:1:
/usr/include/c++/9/bits/unique_ptr.h:707:5: note: candidate: 'template<class _Tp, class _Dp, class _Up, class _Ep> bool std::operator==(const std::unique_ptr<_Tp, _Dp>&, const std::unique_ptr<_Up, _Ep>&)'
707 | operator==(const unique_ptr<_Tp, _Dp>& __x,
| ^~~~~~~~
/usr/include/c++/9/bits/unique_ptr.h:707:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::unique_ptr<_Tp, _Dp>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
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 a.cpp:1:
/usr/include/c++/9/bits/unique_ptr.h:713:5: note: candidate: 'template<class _Tp, class _Dp> bool std::operator==(const std::unique_ptr<_Tp, _Dp>&, std::nullptr_t)'
713 | operator==(const unique_ptr<_Tp, _Dp>& __x, nullptr_t) noexcept
| ^~~~~~~~
/usr/include/c++/9/bits/unique_ptr.h:713:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::unique_ptr<_Tp, _Dp>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
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 a.cpp:1:
/usr/include/c++/9/bits/unique_ptr.h:718:5: note: candidate: 'template<class _Tp, class _Dp> bool std::operator==(std::nullptr_t, const std::unique_ptr<_Tp, _Dp>&)'
718 | operator==(nullptr_t, const unique_ptr<_Tp, _Dp>& __x) noexcept
| ^~~~~~~~
/usr/include/c++/9/bits/unique_ptr.h:718:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: mismatched types 'const std::unique_ptr<_Tp, _Dp>' and 'int'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/iterator:66,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:77,
from a.cpp:1:
/usr/include/c++/9/bits/stream_iterator.h:134:5: note: candidate: 'template<class _Tp, class _CharT, class _Traits, class _Dist> bool std::operator==(const std::istream_iterator<_Tp, _CharT, _Traits, _Dist>&, const std::istream_iterator<_Tp, _CharT, _Traits, _Dist>&)'
134 | operator==(const istream_iterator<_Tp, _CharT, _Traits, _Dist>& __x,
| ^~~~~~~~
/usr/include/c++/9/bits/stream_iterator.h:134:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::istream_iterator<_Tp, _CharT, _Traits, _Dist>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/list:63,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:79,
from a.cpp:1:
/usr/include/c++/9/bits/stl_list.h:1991:5: note: candidate: 'template<class _Tp, class _Alloc> bool std::operator==(const std::list<_Tp, _Alloc>&, const std::list<_Tp, _Alloc>&)'
1991 | operator==(const list<_Tp, _Alloc>& __x, const list<_Tp, _Alloc>& __y)
| ^~~~~~~~
/usr/include/c++/9/bits/stl_list.h:1991:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::list<_Tp, _Alloc>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/map:61,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:81,
from a.cpp:1:
/usr/include/c++/9/bits/stl_map.h:1455:5: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc> bool std::operator==(const std::map<_Key, _Tp, _Compare, _Allocator>&, const std::map<_Key, _Tp, _Compare, _Allocator>&)'
1455 | operator==(const map<_Key, _Tp, _Compare, _Alloc>& __x,
| ^~~~~~~~
/usr/include/c++/9/bits/stl_map.h:1455:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::map<_Key, _Tp, _Compare, _Allocator>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/map:62,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:81,
from a.cpp:1:
/usr/include/c++/9/bits/stl_multimap.h:1119:5: note: candidate: 'template<class _Key, class _Tp, class _Compare, class _Alloc> bool std::operator==(const std::multimap<_Key, _Tp, _Compare, _Allocator>&, const std::multimap<_Key, _Tp, _Compare, _Allocator>&)'
1119 | operator==(const multimap<_Key, _Tp, _Compare, _Alloc>& __x,
| ^~~~~~~~
/usr/include/c++/9/bits/stl_multimap.h:1119:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::multimap<_Key, _Tp, _Compare, _Allocator>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/bits/shared_ptr.h:52,
from /usr/include/c++/9/memory:81,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:82,
from a.cpp:1:
/usr/include/c++/9/bits/shared_ptr_base.h:1412:5: note: candidate: 'template<class _Tp1, class _Tp2, __gnu_cxx::_Lock_policy _Lp> bool std::operator==(const std::__shared_ptr<_Tp1, _Lp>&, const std::__shared_ptr<_Tp2, _Lp>&)'
1412 | operator==(const __shared_ptr<_Tp1, _Lp>& __a,
| ^~~~~~~~
/usr/include/c++/9/bits/shared_ptr_base.h:1412:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::__shared_ptr<_Tp1, _Lp>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/bits/shared_ptr.h:52,
from /usr/include/c++/9/memory:81,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:82,
from a.cpp:1:
/usr/include/c++/9/bits/shared_ptr_base.h:1418:5: note: candidate: 'template<class _Tp, __gnu_cxx::_Lock_policy _Lp> bool std::operator==(const std::__shared_ptr<_Tp, _Lp>&, std::nullptr_t)'
1418 | operator==(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
| ^~~~~~~~
/usr/include/c++/9/bits/shared_ptr_base.h:1418:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::__shared_ptr<_Tp, _Lp>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/bits/shared_ptr.h:52,
from /usr/include/c++/9/memory:81,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:82,
from a.cpp:1:
/usr/include/c++/9/bits/shared_ptr_base.h:1423:5: note: candidate: 'template<class _Tp, __gnu_cxx::_Lock_policy _Lp> bool std::operator==(std::nullptr_t, const std::__shared_ptr<_Tp, _Lp>&)'
1423 | operator==(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
| ^~~~~~~~
/usr/include/c++/9/bits/shared_ptr_base.h:1423:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: mismatched types 'const std::__shared_ptr<_Tp, _Lp>' and 'int'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/memory:81,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:82,
from a.cpp:1:
/usr/include/c++/9/bits/shared_ptr.h:383:5: note: candidate: 'template<class _Tp, class _Up> bool std::operator==(const std::shared_ptr<_Tp>&, const std::shared_ptr<_Tp>&)'
383 | operator==(const shared_ptr<_Tp>& __a, const shared_ptr<_Up>& __b) noexcept
| ^~~~~~~~
/usr/include/c++/9/bits/shared_ptr.h:383:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::shared_ptr<_Tp>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/memory:81,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:82,
from a.cpp:1:
/usr/include/c++/9/bits/shared_ptr.h:388:5: note: candidate: 'template<class _Tp> bool std::operator==(const std::shared_ptr<_Tp>&, std::nullptr_t)'
388 | operator==(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
| ^~~~~~~~
/usr/include/c++/9/bits/shared_ptr.h:388:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::shared_ptr<_Tp>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/memory:81,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:82,
from a.cpp:1:
/usr/include/c++/9/bits/shared_ptr.h:393:5: note: candidate: 'template<class _Tp> bool std::operator==(std::nullptr_t, const std::shared_ptr<_Tp>&)'
393 | operator==(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
| ^~~~~~~~
/usr/include/c++/9/bits/shared_ptr.h:393:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: mismatched types 'const std::shared_ptr<_Tp>' and 'int'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/queue:64,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:86,
from a.cpp:1:
/usr/include/c++/9/bits/stl_queue.h:338:5: note: candidate: 'template<class _Tp, class _Seq> bool std::operator==(const std::queue<_Tp, _Seq>&, const std::queue<_Tp, _Seq>&)'
338 | operator==(const queue<_Tp, _Seq>& __x, const queue<_Tp, _Seq>& __y)
| ^~~~~~~~
/usr/include/c++/9/bits/stl_queue.h:338:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::queue<_Tp, _Seq>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/set:61,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:87,
from a.cpp:1:
/usr/include/c++/9/bits/stl_set.h:979:5: note: candidate: 'template<class _Key, class _Compare, class _Alloc> bool std::operator==(const std::set<_Key, _Compare, _Allocator>&, const std::set<_Key, _Compare, _Allocator>&)'
979 | operator==(const set<_Key, _Compare, _Alloc>& __x,
| ^~~~~~~~
/usr/include/c++/9/bits/stl_set.h:979:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::set<_Key, _Compare, _Allocator>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/set:62,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:87,
from a.cpp:1:
/usr/include/c++/9/bits/stl_multiset.h:964:5: note: candidate: 'template<class _Key, class _Compare, class _Alloc> bool std::operator==(const std::multiset<_Key, _Compare, _Allocator>&, const std::multiset<_Key, _Compare, _Allocator>&)'
964 | operator==(const multiset<_Key, _Compare, _Alloc>& __x,
| ^~~~~~~~
/usr/include/c++/9/bits/stl_multiset.h:964:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::multiset<_Key, _Compare, _Allocator>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/stack:61,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:89,
from a.cpp:1:
/usr/include/c++/9/bits/stl_stack.h:313:5: note: candidate: 'template<class _Tp, class _Seq> bool std::operator==(const std::stack<_Tp, _Seq>&, const std::stack<_Tp, _Seq>&)'
313 | operator==(const stack<_Tp, _Seq>& __x, const stack<_Tp, _Seq>& __y)
| ^~~~~~~~
/usr/include/c++/9/bits/stl_stack.h:313:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::stack<_Tp, _Seq>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/valarray:603,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:95,
from a.cpp:1:
/usr/include/c++/9/bits/valarray_after.h:417:5: note: candidate: 'template<class _Dom1, class _Dom2> std::_Expr<std::__detail::_BinClos<std::__equal_to, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__equal_to, typename _Dom1::value_type>::result_type> std::operator==(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const std::_Expr<_Dom2, typename _Dom2::value_type>&)'
417 | _DEFINE_EXPR_BINARY_OPERATOR(==, __equal_to)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/9/bits/valarray_after.h:417:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/valarray:603,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:95,
from a.cpp:1:
/usr/include/c++/9/bits/valarray_after.h:417:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__equal_to, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__equal_to, typename _Dom1::value_type>::result_type> std::operator==(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)'
417 | _DEFINE_EXPR_BINARY_OPERATOR(==, __equal_to)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/9/bits/valarray_after.h:417:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/valarray:603,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:95,
from a.cpp:1:
/usr/include/c++/9/bits/valarray_after.h:417:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__equal_to, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__equal_to, typename _Dom1::value_type>::result_type> std::operator==(const typename _Dom::value_type&, const std::_Expr<_Dom1, typename _Dom1::value_type>&)'
417 | _DEFINE_EXPR_BINARY_OPERATOR(==, __equal_to)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/9/bits/valarray_after.h:417:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/valarray:603,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:95,
from a.cpp:1:
/usr/include/c++/9/bits/valarray_after.h:417:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__equal_to, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__equal_to, typename _Dom1::value_type>::result_type> std::operator==(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const std::valarray<typename _Dom::value_type>&)'
417 | _DEFINE_EXPR_BINARY_OPERATOR(==, __equal_to)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/9/bits/valarray_after.h:417:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/valarray:603,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:95,
from a.cpp:1:
/usr/include/c++/9/bits/valarray_after.h:417:5: note: candidate: 'template<class _Dom> std::_Expr<std::__detail::_BinClos<std::__equal_to, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__equal_to, typename _Dom1::value_type>::result_type> std::operator==(const std::valarray<typename _Dom::value_type>&, const std::_Expr<_Dom1, typename _Dom1::value_type>&)'
417 | _DEFINE_EXPR_BINARY_OPERATOR(==, __equal_to)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/9/bits/valarray_after.h:417:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:95,
from a.cpp:1:
/usr/include/c++/9/valarray:1197:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__equal_to, std::_ValArray, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__equal_to, _Tp>::result_type> std::operator==(const std::valarray<_Tp>&, const std::valarray<_Tp>&)'
1197 | _DEFINE_BINARY_OPERATOR(==, __equal_to)
| ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/9/valarray:1197:1: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::valarray<_Tp>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:95,
from a.cpp:1:
/usr/include/c++/9/valarray:1197:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__equal_to, std::_ValArray, std::_Constant, _Tp, _Tp>, typename std::__fun<std::__equal_to, _Tp>::result_type> std::operator==(const std::valarray<_Tp>&, const typename std::valarray<_Tp>::value_type&)'
1197 | _DEFINE_BINARY_OPERATOR(==, __equal_to)
| ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/9/valarray:1197:1: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::valarray<_Tp>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:95,
from a.cpp:1:
/usr/include/c++/9/valarray:1197:1: note: candidate: 'template<class _Tp> std::_Expr<std::__detail::_BinClos<std::__equal_to, std::_Constant, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__equal_to, _Tp>::result_type> std::operator==(const typename std::valarray<_Tp>::value_type&, const std::valarray<_Tp>&)'
1197 | _DEFINE_BINARY_OPERATOR(==, __equal_to)
| ^~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/9/valarray:1197:1: note: template argument deduction/substitution failed:
a.cpp:21:28: note: mismatched types 'const std::valarray<_Tp>' and 'int'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/forward_list:40,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:104,
from a.cpp:1:
/usr/include/c++/9/bits/forward_list.tcc:393:5: note: candidate: 'template<class _Tp, class _Alloc> bool std::operator==(const std::forward_list<_Tp, _Alloc>&, const std::forward_list<_Tp, _Alloc>&)'
393 | operator==(const forward_list<_Tp, _Alloc>& __lx,
| ^~~~~~~~
/usr/include/c++/9/bits/forward_list.tcc:393:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::forward_list<_Tp, _Alloc>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/future:39,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:105,
from a.cpp:1:
/usr/include/c++/9/thread:276:3: note: candidate: 'bool std::operator==(std::thread::id, std::thread::id)'
276 | operator==(thread::id __x, thread::id __y) noexcept
| ^~~~~~~~
/usr/include/c++/9/thread:276:25: note: no known conversion for argument 1 from 'std::basic_istream<char>' to 'std::thread::id'
276 | operator==(thread::id __x, thread::id __y) noexcept
| ~~~~~~~~~~~^~~
In file included from /usr/include/c++/9/random:51,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:108,
from a.cpp:1:
/usr/include/c++/9/bits/random.tcc:1884:5: note: candidate: 'template<class _RealType1> bool std::operator==(const std::normal_distribution<_RealType>&, const std::normal_distribution<_RealType>&)'
1884 | operator==(const std::normal_distribution<_RealType>& __d1,
| ^~~~~~~~
/usr/include/c++/9/bits/random.tcc:1884:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::normal_distribution<_RealType>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/regex:62,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110,
from a.cpp:1:
/usr/include/c++/9/bits/regex.h:1026:5: note: candidate: 'template<class _BiIter> bool std::operator==(const std::sub_match<_BiIter>&, const std::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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::sub_match<_BiIter>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/regex:62,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110,
from a.cpp:1:
/usr/include/c++/9/bits/regex.h:1099:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::operator==(std::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>&, const std::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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'std::__sub_match_string<_Bi_iter, _Ch_traits, _Ch_alloc>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/regex:62,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110,
from a.cpp:1:
/usr/include/c++/9/bits/regex.h:1173:5: note: candidate: 'template<class _Bi_iter, class _Ch_traits, class _Ch_alloc> bool std::operator==(const std::sub_match<_BiIter>&, std::__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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::sub_match<_BiIter>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/regex:62,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110,
from a.cpp:1:
/usr/include/c++/9/bits/regex.h:1247:5: note: candidate: 'template<class _Bi_iter> bool std::operator==(const typename std::iterator_traits<_Iter>::value_type*, const std::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:
a.cpp:21:28: note: mismatched types 'const std::sub_match<_BiIter>' and 'int'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/regex:62,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110,
from a.cpp:1:
/usr/include/c++/9/bits/regex.h:1321:5: note: candidate: 'template<class _Bi_iter> bool std::operator==(const std::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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::sub_match<_BiIter>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/regex:62,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110,
from a.cpp:1:
/usr/include/c++/9/bits/regex.h:1395:5: note: candidate: 'template<class _Bi_iter> bool std::operator==(const typename std::iterator_traits<_Iter>::value_type&, const std::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:
a.cpp:21:28: note: mismatched types 'const std::sub_match<_BiIter>' and 'int'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/regex:62,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110,
from a.cpp:1:
/usr/include/c++/9/bits/regex.h:1473:5: note: candidate: 'template<class _Bi_iter> bool std::operator==(const std::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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::sub_match<_BiIter>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/regex:62,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:110,
from a.cpp:1:
/usr/include/c++/9/bits/regex.h:1991:5: note: candidate: 'template<class _Bi_iter, class _Alloc> bool std::operator==(const std::match_results<_BiIter, _Alloc>&, const std::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:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::match_results<_BiIter, _Alloc>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:111,
from a.cpp:1:
/usr/include/c++/9/scoped_allocator:489:5: note: candidate: 'template<class _OutA1, class _OutA2, class ... _InA> bool std::operator==(const std::scoped_allocator_adaptor<_OutA1, _InA ...>&, const std::scoped_allocator_adaptor<_InnerHead, _InnerTail ...>&)'
489 | operator==(const scoped_allocator_adaptor<_OutA1, _InA...>& __a,
| ^~~~~~~~
/usr/include/c++/9/scoped_allocator:489:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::scoped_allocator_adaptor<_OutA1, _InA ...>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/unordered_set:47,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:118,
from a.cpp:1:
/usr/include/c++/9/bits/unordered_set.h:1703:5: note: candidate: 'template<class _Value1, class _Hash1, class _Pred1, class _Alloc1> bool std::operator==(const std::unordered_set<_Value1, _Hash1, _Pred1, _Alloc1>&, const std::unordered_set<_Value1, _Hash1, _Pred1, _Alloc1>&)'
1703 | operator==(const unordered_set<_Value, _Hash, _Pred, _Alloc>& __x,
| ^~~~~~~~
/usr/include/c++/9/bits/unordered_set.h:1703:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::unordered_set<_Value1, _Hash1, _Pred1, _Alloc1>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/c++/9/unordered_set:47,
from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:118,
from a.cpp:1:
/usr/include/c++/9/bits/unordered_set.h:1715:5: note: candidate: 'template<class _Value1, class _Hash1, class _Pred1, class _Alloc1> bool std::operator==(const std::unordered_multiset<_Value1, _Hash1, _Pred1, _Alloc1>&, const std::unordered_multiset<_Value1, _Hash1, _Pred1, _Alloc1>&)'
1715 | operator==(const unordered_multiset<_Value, _Hash, _Pred, _Alloc>& __x,
| ^~~~~~~~
/usr/include/c++/9/bits/unordered_set.h:1715:5: note: template argument deduction/substitution failed:
a.cpp:21:28: note: 'std::basic_istream<char>' is not derived from 'const std::unordered_multiset<_Value1, _Hash1, _Pred1, _Alloc1>'
21 | if(dfs() &&(cin>>c)== -1)cout<<a;
| ^
In file included from /usr/include/x86_64-linux-gnu/c++/9/bits/stdc++.h:133,
from a.cpp:1:
/usr/include/c++/9/variant:1177:3: note: candidate: 'template<class ... _Types> constexpr bool std::operator==(const std::variant<_Types ...>&, const std::
666
有奖问答：请问你看这个编译错误的信息用了多长时间？
90s