“#P105. 计算(a+b)/c的值”提交后怎么······ 0 Compile Error foo.cc: In function 'int main()': foo.cc:5:8: error: no match for 'operator<<' (operand types are 'std::istream' {aka 'std::basic_istream'} and 'int') 5 | cin<<a<<b<c; | ~^ | | | | | int | std::istream {aka std::basic_istream} foo.cc:5:8: note: there are 27 candidates 5 | cin<<a<<b<c; | ~^ In file included from /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/string:56, from /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bitset:54, from /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/x86_64-unknown-linux-gnu/bits/stdc++.h:54, from foo.cc:1: /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/basic_string.h:4367:5: note: candidate 1: 'template<class _CharT, class _Traits, class _Alloc> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, const __cxx11::basic_string<_CharT, _Traits, _Alloc>&)' 4367 | operator<<(basic_ostream<_CharT, _Traits>& __os, | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/basic_string.h:4367:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bitset:1692:5: note: candidate 2: 'template<class _CharT, class _Traits, long unsigned int _Nb> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, const bitset<_Nb>&)' 1692 | operator<<(std::basic_ostream<_CharT, _Traits>& __os, | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bitset:1692:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a<<b<c; | ^ In file included from /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/ostream:42, from /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/istream:43, from /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/sstream:42, from /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/complex:50, from /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/x86_64-unknown-linux-gnu/bits/stdc++.h:141: /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:626:5: note: candidate 3: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, _CharT)' 626 | operator<<(basic_ostream<_CharT, _Traits>& __out, _CharT __c) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:626:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:636:5: note: candidate 4: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, char)' 636 | operator<<(basic_ostream<_CharT, _Traits>& __out, char __c) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:636:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:642:5: note: candidate 5: 'template std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, char)' 642 | operator<<(basic_ostream<char, _Traits>& __out, char __c) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:642:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<char, _Traits>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:653:5: note: candidate 6: 'template std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, signed char)' 653 | operator<<(basic_ostream<char, _Traits>& __out, signed char __c) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:653:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<char, _Traits>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:658:5: note: candidate 7: 'template std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, unsigned char)' 658 | operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:658:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<char, _Traits>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:717:5: note: candidate 8: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, const _CharT)' 717 | operator<<(basic_ostream<_CharT, _Traits>& __out, const _CharT* __s) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:717:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a<<b<c; | ^ In file included from /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/ostream:294: /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.tcc:311:5: note: candidate 9: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, const char*)' 311 | operator<<(basic_ostream<_CharT, _Traits>& __out, const char* __s) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.tcc:311:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:734:5: note: candidate 10: 'template std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, const char*)' 734 | operator<<(basic_ostream<char, _Traits>& __out, const char* __s) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:734:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<char, _Traits>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:747:5: note: candidate 11: 'template std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, const signed char*)' 747 | operator<<(basic_ostream<char, _Traits>& __out, const signed char* __s) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:747:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<char, _Traits>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:752:5: note: candidate 12: 'template std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, const unsigned char*)' 752 | operator<<(basic_ostream<char, _Traits>& __out, const unsigned char* __s) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/ostream.h:752:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<char, _Traits>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/complex:597:5: note: candidate 13: 'template<class _Tp, class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, const complex<_Tp>&)' 597 | operator<<(basic_ostream<_CharT, _Traits>& __os, const complex<_Tp>& __x) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/complex:597:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a<<b<c; | ^ In file included from /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/x86_64-unknown-linux-gnu/bits/stdc++.h:146: /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/iomanip:89:5: note: candidate 14: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, _Resetiosflags)' 89 | operator<<(basic_ostream<_CharT, _Traits>& __os, _Resetiosflags __f) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/iomanip:89:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/iomanip:119:5: note: candidate 15: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, _Setiosflags)' 119 | operator<<(basic_ostream<_CharT, _Traits>& __os, _Setiosflags __f) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/iomanip:119:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/iomanip:153:5: note: candidate 16: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, _Setbase)' 153 | operator<<(basic_ostream<_CharT, _Traits>& __os, _Setbase __f) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/iomanip:153:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/iomanip:190:5: note: candidate 17: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, _Setfill<_CharT>)' 190 | operator<<(basic_ostream<_CharT, _Traits>& __os, _Setfill<_CharT> __f) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/iomanip:190:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/iomanip:220:5: note: candidate 18: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, _Setprecision)' 220 | operator<<(basic_ostream<_CharT, _Traits>& __os, _Setprecision __f) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/iomanip:220:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/iomanip:250:5: note: candidate 19: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, _Setw)' 250 | operator<<(basic_ostream<_CharT, _Traits>& __os, _Setw __f) | ^~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/iomanip:250:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a<<b<c; | ^ In file included from /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/valarray:607, from /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/x86_64-unknown-linux-gnu/bits/stdc++.h:169: /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/valarray_after.h:415:5: note: candidate 20: 'template<class _Dom1, class _Dom2> std::_Expr<std::__detail::_BinClos<std::__shift_left, std::_Expr, std::_Expr, _Dom1, _Dom2>, typename std::__fun<std::__shift_left, typename _Dom1::value_type>::result_type> std::operator<<(const _Expr<_Dom1, typename _Dom1::value_type>&, const _Expr<_Dom2, typename _Dom2::value_type>&)' 415 | _DEFINE_EXPR_BINARY_OPERATOR(<<, struct std::__shift_left) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/valarray_after.h:415:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/valarray_after.h:415:5: note: candidate 21: 'template std::_Expr<std::__detail::_BinClos<std::__shift_left, std::_Expr, std::_Constant, _Dom, typename _Dom::value_type>, typename std::__fun<std::__shift_left, typename _Dom1::value_type>::result_type> std::operator<<(const _Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&)' 415 | _DEFINE_EXPR_BINARY_OPERATOR(<<, struct std::__shift_left) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/valarray_after.h:415:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/valarray_after.h:415:5: note: candidate 22: 'template std::_Expr<std::__detail::_BinClos<std::__shift_left, std::_Constant, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__shift_left, typename _Dom1::value_type>::result_type> std::operator<<(const typename _Dom::value_type&, const _Expr<_Dom1, typename _Dom1::value_type>&)' 415 | _DEFINE_EXPR_BINARY_OPERATOR(<<, struct std::__shift_left) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/valarray_after.h:415:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/valarray_after.h:415:5: note: candidate 23: 'template std::_Expr<std::__detail::_BinClos<std::__shift_left, std::_Expr, std::_ValArray, _Dom, typename _Dom::value_type>, typename std::__fun<std::__shift_left, typename _Dom1::value_type>::result_type> std::operator<<(const _Expr<_Dom1, typename _Dom1::value_type>&, const valarray&)' 415 | _DEFINE_EXPR_BINARY_OPERATOR(<<, struct std::__shift_left) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/valarray_after.h:415:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/valarray_after.h:415:5: note: candidate 24: 'template std::_Expr<std::__detail::_BinClos<std::__shift_left, std::_ValArray, std::_Expr, typename _Dom::value_type, _Dom>, typename std::__fun<std::__shift_left, typename _Dom1::value_type>::result_type> std::operator<<(const valarray&, const _Expr<_Dom1, typename _Dom1::value_type>&)' 415 | _DEFINE_EXPR_BINARY_OPERATOR(<<, struct std::__shift_left) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/bits/valarray_after.h:415:5: note: template argument deduction/substitution failed: foo.cc:5:10: note: mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/valarray:1206:1: note: candidate 25: 'template std::_Expr<std::__detail::_BinClos<std::__shift_left, std::_ValArray, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__shift_left, _Tp>::result_type> std::operator<<(const valarray<_Tp>&, const valarray<_Tp>&)' 1206 | _DEFINE_BINARY_OPERATOR(<<, __shift_left) | ^~~~~~~~~~~~~~~~~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/valarray:1206:1: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'const std::valarray<_Tp>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/valarray:1206:1: note: candidate 26: 'template std::_Expr<std::__detail::_BinClos<std::__shift_left, std::_ValArray, std::_Constant, _Tp, _Tp>, typename std::__fun<std::__shift_left, _Tp>::result_type> std::operator<<(const valarray<_Tp>&, const typename valarray<_Tp>::value_type&)' 1206 | _DEFINE_BINARY_OPERATOR(<<, __shift_left) | ^~~~~~~~~~~~~~~~~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/valarray:1206:1: note: template argument deduction/substitution failed: foo.cc:5:10: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'const std::valarray<_Tp>' 5 | cin<<a<<b<c; | ^ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/valarray:1206:1: note: candidate 27: 'template std::_Expr<std::__detail::_BinClos<std::__shift_left, std::_Constant, std::_ValArray, _Tp, _Tp>, typename std::__fun<std::__shift_left, _Tp>::result_type> std::operator<<(const typename valarray<_Tp>::value_type&, const valarray<_Tp>&)' 1206 | _DEFINE_BINARY_OPERATOR(<<, __shift_left) | ^~~~~~~~~~~~~~~~~~~~~~~ /nix/store/lvwga6ivl1d4lnw0zis9ajs0rqx9gp4i-gcc-15.2.0/include/c++/15.2.0/valarray:1206:1: note: template argument deduction/substitution failed: foo.cc:5:10: note: mismatched types 'const std::valarray<_Tp>' and 'int' 5 | cin<<a<<b<c; | ^