In file included from /usr/include/c++/7/algorithm:62:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:65, from Main.cc:1: /usr/include/c++/7/bits/stl_algo.h: In instantiation of ‘_Iterator std::__find_if(_Iterator, _Iterator, _Predicate) [with _Iterator = int; _Predicate = __gnu_cxx::__ops::_Iter_equals_val]’: /usr/include/c++/7/bits/stl_algo.h:3907:28: required from ‘_IIter std::find(_IIter, _IIter, const _Tp&) [with _IIter = int; _Tp = bool]’ Main.cc:47:19: required from here /usr/include/c++/7/bits/stl_algo.h:162:34: error: no matching function for call to ‘__iterator_category(int&)’ std::__iterator_category(__first)); ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~ In file included from /usr/include/c++/7/bits/stl_algobase.h:65:0, from /usr/include/c++/7/bits/char_traits.h:39, from /usr/include/c++/7/ios:40, from /usr/include/c++/7/istream:38, from /usr/include/c++/7/sstream:38, from /usr/include/c++/7/complex:45, from /usr/include/c++/7/ccomplex:39, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52, from Main.cc:1: /usr/include/c++/7/bits/stl_iterator_base_types.h:205:5: note: candidate: template constexpr typename std::iterator_traits<_Iterator>::iterator_category std::__iterator_category(const _Iter&) __iterator_category(const _Iter&) ^~~~~~~~~~~~~~~~~~~ /usr/include/c++/7/bits/stl_iterator_base_types.h:205:5: note: template argument deduction/substitution failed: /usr/include/c++/7/bits/stl_iterator_base_types.h: In substitution of ‘template constexpr typename std::iterator_traits<_Iterator>::iterator_category std::__iterator_category(const _Iter&) [with _Iter = int]’: /usr/include/c++/7/bits/stl_algo.h:162:34: required from ‘_Iterator std::__find_if(_Iterator, _Iterator, _Predicate) [with _Iterator = int; _Predicate = __gnu_cxx::__ops::_Iter_equals_val]’ /usr/include/c++/7/bits/stl_algo.h:3907:28: required from ‘_IIter std::find(_IIter, _IIter, const _Tp&) [with _IIter = int; _Tp = bool]’ Main.cc:47:19: required from here /usr/include/c++/7/bits/stl_iterator_base_types.h:205:5: error: no type named ‘iterator_category’ in ‘struct std::iterator_traits’