In file included from /usr/include/c++/11/map:60,
from /usr/include/x86_64-linux-gnu/c++/11/bits/stdc++.h:81,
from commuter_pass.cpp:1:
/usr/include/c++/11/bits/stl_tree.h: In instantiation of 'struct std::_Rb_tree_key_compare<bool(int, int)>':
/usr/include/c++/11/bits/stl_tree.h:660:9: required from 'struct std::_Rb_tree<int, int, std::_Identity<int>, bool(int, int), std::allocator<int> >::_Rb_tree_impl<bool(int, int), false>'
/usr/include/c++/11/bits/stl_tree.h:706:31: required from 'class std::_Rb_tree<int, int, std::_Identity<int>, bool(int, int), std::allocator<int> >'
/usr/include/c++/11/bits/stl_set.h:133:17: required from 'class std::set<int, bool(int, int)>'
commuter_pass.cpp:17:34: required from here
/usr/include/c++/11/bits/stl_tree.h:144:33: error: data member 'std::_Rb_tree_key_compare<bool(int, int)>::_M_key_compare' invalidly declared function type
144 | _Key_compare _M_key_compare;
| ^~~~~~~~~~~~~~
/usr/include/c++/11/bits/stl_tree.h: In instantiation of 'class std::_Rb_tree<int, int, std::_Identity<int>, bool(int, int), std::allocator<int> >':
/usr/include/c++/11/bits/stl_set.h:133:17: required from 'class std::set<int, bool(int, int)>'
commuter_pass.cpp:17:34: required from here
/usr/include/c++/11/bits/stl_tree.h:991:7: error: function returning a function
991 | key_comp() const
| ^~~~~~~~
In file included from /usr/include/c++/11/set:61,
from /usr/include/x86_64-linux-gnu/c++/11/bits/stdc++.h:87,
from commuter_pass.cpp:1:
/usr/include/c++/11/bits/stl_set.h: In instantiation of 'class std::set<int, bool(int, int)>':
commuter_pass.cpp:17:34: required from here
/usr/include/c++/11/bits/stl_set.h:327:7: error: function returning a function
327 | key_comp() const
| ^~~~~~~~
/usr/include/c++/11/bits/stl_set.h:331:7: error: function returning a function
331 | value_comp() const
| ^~~~~~~~~~
In file included from /usr/include/c++/11/set:62,
from /usr/include/x86_64-linux-gnu/c++/11/bits/stdc++.h:87,
from commuter_pass.cpp:1:
/usr/include/c++/11/bits/stl_multiset.h: In instantiation of 'class std::multiset<int, bool(int, int)>':
commuter_pass.cpp:41:39: required from here
/usr/include/c++/11/bits/stl_multiset.h:323:7: error: function returning a function
323 | key_comp() const
| ^~~~~~~~
/usr/include/c++/11/bits/stl_multiset.h:327:7: error: function returning a function
327 | value_comp() const
| ^~~~~~~~~~