Eroare de compilare: user.cpp: In function ‘int main()’: user.cpp:15:2: error: no match for ‘operator<<’ (operand types are ‘std::ifstream {aka std::basic_ifstream<char>}’ and ‘int’) f<<1<<" "; ~^~~ user.cpp:15:2: note: candidate: operator<<(int, int) <built-in> user.cpp:15:2: note: no known conversion for argument 1 from ‘std::ifstream {aka std::basic_ifstream<char>}’ to ‘int’ In file included from /usr/include/c++/6/string:52:0, from /usr/include/c++/6/bits/locale_classes.h:40, from /usr/include/c++/6/bits/ios_base.h:41, from /usr/include/c++/6/ios:42, from /usr/include/c++/6/istream:38, from /usr/include/c++/6/fstream:38, from user.cpp:1: /usr/include/c++/6/bits/basic_string.h:5340:5: note: candidate: template<class _CharT, class _Traits, class _Alloc> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&) operator<<(basic_ostream<_CharT, _Traits>& __os, ^~~~~~~~ /usr/include/c++/6/bits/basic_string.h:5340:5: note: template argument deduction/substitution failed: user.cpp:15:4: note: ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘std::basic_ostream<_CharT, _Traits>’ f<<1<<" "; ^ In file included from /usr/include/c++/6/bits/ios_base.h:46:0, from /usr/include/c++/6/ios:42, from /usr/include/c++/6/istream:38, from /usr/include/c++/6/fstream:38, from user.cpp:1: /usr/include/c++/6/system_error:209:5: note: candidate: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, const std::error_code&) operator<<(basic_ostream<_CharT, _Traits>& __os, const error_code& __e) ^~~~~~~~ /usr/include/c++/6/system_error:209:5: note: template argument deduction/substitution failed: user.cpp:15:4: note: ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘std::basic_ostream<_CharT, _Traits>’ f<<1<<" "; ^ In file included from /usr/include/c++/6/istream:39:0, from /usr/include/c++/6/fstream:38, from user.cpp:1: /usr/include/c++/6/ostream:497:5: note: candidate: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, _CharT) operator<<(basic_ostream<_CharT, _Traits>& __out, _CharT __c) ^~~~~~~~ /usr/include/c++/6/ostream:497:5: note: template argument deduction/substitution failed: user.cpp:15:4: note: ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘std::basic_ostream<_CharT, _Traits>’ f<<1<<" "; ^ In file included from /usr/include/c++/6/istream:39:0, from /usr/include/c++/6/fstream:38, from user.cpp:1: /usr/include/c++/6/ostream:502:5: note: candidate: template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(std::basic_ostream<_CharT, _Traits>&, char) operator<<(basic_ostream<_CharT, _Traits>& __out, char __c) ^~~~~~~~ /usr/include/c++/6/ostream:502:5: note: template argument deduction/substitution failed: user.cpp:15:4: note: ‘std::ifstream {aka std::basic_ifstream<char>}’ is not derived from ‘std::basic_ostream<_CharT, _Traits>’