foo.cc: In function 'int main()': foo.cc:5:12: error: no match for 'operator<<' (operand types are 'std::istream' {aka 'std::basic_istream'} and 'long long int') 5 | cin<<a; | ~^ | | | | | long long int | std::istream {aka std::basic_istream} In file included from /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/string:54, from /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bitset:52, from /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/x86_64-unknown-linux-gnu/bits/stdc++.h:52, from foo.cc:1: /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bits/basic_string.h:4032:5: note: candidate: '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>&)' 4032 | operator<<(basic_ostream<_CharT, _Traits>& __os, | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bits/basic_string.h:4032:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bitset:1683:5: note: candidate: 'template<class _CharT, class _Traits, long unsigned int _Nb> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, const bitset<_Nb>&)' 1683 | operator<<(std::basic_ostream<_CharT, _Traits>& __os, | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bitset:1683:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a; | ^ In file included from /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/istream:41, from /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/sstream:40, from /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/complex:45, from /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/x86_64-unknown-linux-gnu/bits/stdc++.h:138: /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:554:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, _CharT)' 554 | operator<<(basic_ostream<_CharT, _Traits>& __out, _CharT __c) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:554:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:564:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, char)' 564 | operator<<(basic_ostream<_CharT, _Traits>& __out, char __c) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:564:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:570:5: note: candidate: 'template std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, char)' 570 | operator<<(basic_ostream<char, _Traits>& __out, char __c) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:570:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<char, _Traits>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:581:5: note: candidate: 'template std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, signed char)' 581 | operator<<(basic_ostream<char, _Traits>& __out, signed char __c) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:581:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<char, _Traits>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:586:5: note: candidate: 'template std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, unsigned char)' 586 | operator<<(basic_ostream<char, _Traits>& __out, unsigned char __c) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:586:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<char, _Traits>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:645:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, const _CharT*)' 645 | operator<<(basic_ostream<_CharT, _Traits>& __out, const _CharT* __s) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:645:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a; | ^ In file included from /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:880: /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bits/ostream.tcc:307:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, const char*)' 307 | operator<<(basic_ostream<_CharT, _Traits>& __out, const char* __s) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bits/ostream.tcc:307:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:662:5: note: candidate: 'template std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, const char*)' 662 | operator<<(basic_ostream<char, _Traits>& __out, const char* __s) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:662:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<char, _Traits>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:675:5: note: candidate: 'template std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, const signed char*)' 675 | operator<<(basic_ostream<char, _Traits>& __out, const signed char* __s) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:675:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<char, _Traits>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:680:5: note: candidate: 'template std::basic_ostream<char, _Traits>& std::operator<<(basic_ostream<char, _Traits>&, const unsigned char*)' 680 | operator<<(basic_ostream<char, _Traits>& __out, const unsigned char* __s) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/ostream:680:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<char, _Traits>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/complex:558:5: note: candidate: 'template<class _Tp, class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, const complex<_Tp>&)' 558 | operator<<(basic_ostream<_CharT, _Traits>& __os, const complex<_Tp>& __x) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/complex:558:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a; | ^ In file included from /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/x86_64-unknown-linux-gnu/bits/stdc++.h:143: /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/iomanip:81:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, _Resetiosflags)' 81 | operator<<(basic_ostream<_CharT, _Traits>& __os, _Resetiosflags __f) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/iomanip:81:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/iomanip:111:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, _Setiosflags)' 111 | operator<<(basic_ostream<_CharT, _Traits>& __os, _Setiosflags __f) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/iomanip:111:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/iomanip:145:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, _Setbase)' 145 | operator<<(basic_ostream<_CharT, _Traits>& __os, _Setbase __f) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/iomanip:145:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/iomanip:180:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, _Setfill<_CharT>)' 180 | operator<<(basic_ostream<_CharT, _Traits>& __os, _Setfill<_CharT> __f) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/iomanip:180:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/iomanip:210:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, _Setprecision)' 210 | operator<<(basic_ostream<_CharT, _Traits>& __os, _Setprecision __f) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/iomanip:210:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/iomanip:240:5: note: candidate: 'template<class _CharT, class _Traits> std::basic_ostream<_CharT, _Traits>& std::operator<<(basic_ostream<_CharT, _Traits>&, _Setw)' 240 | operator<<(basic_ostream<_CharT, _Traits>& __os, _Setw __f) | ^~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/iomanip:240:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'std::basic_ostream<_CharT, _Traits>' 5 | cin<<a; | ^ In file included from /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/valarray:605, from /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/x86_64-unknown-linux-gnu/bits/stdc++.h:166: /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bits/valarray_after.h:413:5: note: candidate: '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>&)' 413 | _DEFINE_EXPR_BINARY_OPERATOR(<<, struct std::__shift_left) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bits/valarray_after.h:413:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bits/valarray_after.h:413:5: note: candidate: '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&)' 413 | _DEFINE_EXPR_BINARY_OPERATOR(<<, struct std::__shift_left) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bits/valarray_after.h:413:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bits/valarray_after.h:413:5: note: candidate: '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>&)' 413 | _DEFINE_EXPR_BINARY_OPERATOR(<<, struct std::__shift_left) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bits/valarray_after.h:413:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'long long int' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bits/valarray_after.h:413:5: note: candidate: '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&)' 413 | _DEFINE_EXPR_BINARY_OPERATOR(<<, struct std::__shift_left) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bits/valarray_after.h:413:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bits/valarray_after.h:413:5: note: candidate: '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>&)' 413 | _DEFINE_EXPR_BINARY_OPERATOR(<<, struct std::__shift_left) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/bits/valarray_after.h:413:5: note: template argument deduction/substitution failed: foo.cc:5:14: note: mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'long long int' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/valarray:1204:1: note: candidate: '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>&)' 1204 | _DEFINE_BINARY_OPERATOR(<<, __shift_left) | ^~~~~~~~~~~~~~~~~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/valarray:1204:1: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'const std::valarray<_Tp>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/valarray:1204:1: note: candidate: '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&)' 1204 | _DEFINE_BINARY_OPERATOR(<<, __shift_left) | ^~~~~~~~~~~~~~~~~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/valarray:1204:1: note: template argument deduction/substitution failed: foo.cc:5:14: note: 'std::istream' {aka 'std::basic_istream'} is not derived from 'const std::valarray<_Tp>' 5 | cin<<a; | ^ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/valarray:1204:1: note: candidate: '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>&)' 1204 | _DEFINE_BINARY_OPERATOR(<<, __shift_left) | ^~~~~~~~~~~~~~~~~~~~~~~ /nix/store/xzfmarrq8x8s4ivpya24rrndqsq2ndiz-gcc-13.3.0/include/c++/13.3.0/valarray:1204:1: note: template argument deduction/substitution failed: foo.cc:5:14: note: mismatched types 'const std::valarray<_Tp>' and 'long long int' 5 | cin<<a; | ^