main.cpp: In function 'int main()': main.cpp:25:15: error: no match for 'operator-' (operand types are 'int' and 'car') a[i]=l-a[i]; ~^~~~~ In file included from /usr/include/c++/7/bits/stl_algobase.h:67:0, 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.cpp:1: /usr/include/c++/7/bits/stl_iterator.h:392:5: note: candidate: template decltype ((__y.base() - __x.base())) std::operator-(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_IteratorR>&) operator-(const reverse_iterator<_IteratorL>& __x, ^~~~~~~~ /usr/include/c++/7/bits/stl_iterator.h:392:5: note: template argument deduction/substitution failed: main.cpp:25:19: note: mismatched types 'const std::reverse_iterator<_Iterator>' and 'int' a[i]=l-a[i]; ^ In file included from /usr/include/c++/7/bits/stl_algobase.h:67:0, 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.cpp:1: /usr/include/c++/7/bits/stl_iterator.h:1194:5: note: candidate: template decltype ((__x.base() - __y.base())) std::operator-(const std::move_iterator<_IteratorL>&, const std::move_iterator<_IteratorR>&) operator-(const move_iterator<_IteratorL>& __x, ^~~~~~~~ /usr/include/c++/7/bits/stl_iterator.h:1194:5: note: template argument deduction/substitution failed: main.cpp:25:19: note: mismatched types 'const std::move_iterator<_IteratorL>' and 'int' a[i]=l-a[i]; ^ In file included from /usr/include/c++/7/ccomplex:39:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52, from main.cpp:1: /usr/include/c++/7/complex:356:5: note: candidate: template std::complex<_Tp> std::operator-(const std::complex<_Tp>&, const std::complex<_Tp>&) operator-(const complex<_Tp>& __x, const complex<_Tp>& __y) ^~~~~~~~ /usr/include/c++/7/complex:356:5: note: template argument deduction/substitution failed: main.cpp:25:19: note: mismatched types 'const std::complex<_Tp>' and 'int' a[i]=l-a[i]; ^ In file included from /usr/include/c++/7/ccomplex:39:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52, from main.cpp:1: /usr/include/c++/7/complex:365:5: note: candidate: template std::complex<_Tp> std::operator-(const std::complex<_Tp>&, const _Tp&) operator-(const complex<_Tp>& __x, const _Tp& __y) ^~~~~~~~ /usr/include/c++/7/complex:365:5: note: template argument deduction/substitution failed: main.cpp:25:19: note: mismatched types 'const std::complex<_Tp>' and 'int' a[i]=l-a[i]; ^ In file included from /usr/include/c++/7/ccomplex:39:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52, from main.cpp:1: /usr/include/c++/7/complex:374:5: note: candidate: template std::complex<_Tp> std::operator-(const _Tp&, const std::complex<_Tp>&) operator-(const _Tp& __x, const complex<_Tp>& __y) ^~~~~~~~ /usr/include/c++/7/complex:374:5: note: template argument deduction/substitution failed: main.cpp:25:19: note: 'car' is not derived from 'const std::complex<_Tp>' a[i]=l-a[i]; ^ In file included from /usr/include/c++/7/ccomplex:39:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:52, from main.cpp:1: /usr/include/c++/7/complex:451:5: note: candidate: template std::complex<_Tp> std::operator-(const std::complex<_Tp>&) operator-(const complex<_Tp>& __x) ^~~~~~~~ /usr/include/c++/7/complex:451:5: note: template argument deduction/substitution failed: main.cpp:25:19: note: mismatched types 'const std::complex<_Tp>' and 'int' a[i]=l-a[i]; ^ In file included from /usr/include/c++/7/deque:64:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:68, from main.cpp:1: /usr/include/c++/7/bits/stl_deque.h:351:5: note: candidate: template typename std::_Deque_iterator<_Tp, _Ref, _Ptr>::difference_type std::operator-(const std::_Deque_iterator<_Tp, _Ref, _Ptr>&, const std::_Deque_iterator<_Tp, _Ref, _Ptr>&) operator-(const _Deque_iterator<_Tp, _Ref, _Ptr>& __x, ^~~~~~~~ /usr/include/c++/7/bits/stl_deque.h:351:5: note: template argument deduction/substitution failed: main.cpp:25:19: note: mismatched types 'const std::_Deque_iterator<_Tp, _Ref, _Ptr>' and 'int' a[i]=l-a[i]; ^ In file included from /usr/include/c++/7/deque:64:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:68, from main.cpp:1: /usr/include/c++/7/bits/stl_deque.h:363:5: note: candidate: template typename std::_Deque_iterator<_Tp, _Ref, _Ptr>::difference_type std::operator-(const std::_Deque_iterator<_Tp, _Ref, _Ptr>&, const std::_Deque_iterator<_Tp, _RefR, _PtrR>&) operator-(const _Deque_iterator<_Tp, _RefL, _PtrL>& __x, ^~~~~~~~ /usr/include/c++/7/bits/stl_deque.h:363:5: note: template argument deduction/substitution failed: main.cpp:25:19: note: mismatched types 'const std::_Deque_iterator<_Tp, _Ref, _Ptr>' and 'int' a[i]=l-a[i]; ^ In file included from /usr/include/c++/7/vector:65:0, from /usr/include/c++/7/queue:61, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:86, from main.cpp:1: /usr/include/c++/7/bits/stl_bvector.h:208:3: note: candidate: std::ptrdiff_t std::operator-(const std::_Bit_iterator_base&, const std::_Bit_iterator_base&) operator-(const _Bit_iterator_base& __x, const _Bit_iterator_base& __y) ^~~~~~~~ /usr/include/c++/7/bits/stl_bvector.h:208:3: note: no known conversion for argument 1 from 'int' to 'const std::_Bit_iterator_base&' In file included from /usr/include/c++/7/valarray:592:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95, from main.cpp:1: /usr/include/c++/7/bits/valarray_after.h:403:5: note: candidate: template std::_Expr, typename std::__fun::result_type> std::operator-(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const std::_Expr<_Dom2, typename _Dom2::value_type>&) _DEFINE_EXPR_BINARY_OPERATOR(-, __minus) ^ /usr/include/c++/7/bits/valarray_after.h:403:5: note: template argument deduction/substitution failed: main.cpp:25:19: note: mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int' a[i]=l-a[i]; ^ In file included from /usr/include/c++/7/valarray:592:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95, from main.cpp:1: /usr/include/c++/7/bits/valarray_after.h:403:5: note: candidate: template std::_Expr, typename std::__fun::result_type> std::operator-(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const typename _Dom::value_type&) _DEFINE_EXPR_BINARY_OPERATOR(-, __minus) ^ /usr/include/c++/7/bits/valarray_after.h:403:5: note: template argument deduction/substitution failed: main.cpp:25:19: note: mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int' a[i]=l-a[i]; ^ In file included from /usr/include/c++/7/valarray:592:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95, from main.cpp:1: /usr/include/c++/7/bits/valarray_after.h:403:5: note: candidate: template std::_Expr, typename std::__fun::result_type> std::operator-(const typename _Dom::value_type&, const std::_Expr<_Dom1, typename _Dom1::value_type>&) _DEFINE_EXPR_BINARY_OPERATOR(-, __minus) ^ /usr/include/c++/7/bits/valarray_after.h:403:5: note: template argument deduction/substitution failed: main.cpp:25:19: note: 'car' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>' a[i]=l-a[i]; ^ In file included from /usr/include/c++/7/valarray:592:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95, from main.cpp:1: /usr/include/c++/7/bits/valarray_after.h:403:5: note: candidate: template std::_Expr, typename std::__fun::result_type> std::operator-(const std::_Expr<_Dom1, typename _Dom1::value_type>&, const std::valarray&) _DEFINE_EXPR_BINARY_OPERATOR(-, __minus) ^ /usr/include/c++/7/bits/valarray_after.h:403:5: note: template argument deduction/substitution failed: main.cpp:25:19: note: mismatched types 'const std::_Expr<_Dom1, typename _Dom1::value_type>' and 'int' a[i]=l-a[i]; ^ In file included from /usr/include/c++/7/valarray:592:0, from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95, from main.cpp:1: /usr/include/c++/7/bits/valarray_after.h:403:5: note: candidate: template std::_Expr, typename std::__fun::result_type> std::operator-(const std::valarray&, const std::_Expr<_Dom1, typename _Dom1::value_type>&) _DEFINE_EXPR_BINARY_OPERATOR(-, __minus) ^ /usr/include/c++/7/bits/valarray_after.h:403:5: note: template argument deduction/substitution failed: main.cpp:25:19: note: 'car' is not derived from 'const std::_Expr<_Dom1, typename _Dom1::value_type>' a[i]=l-a[i]; ^ In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95:0, from main.cpp:1: /usr/include/c++/7/valarray:1173:1: note: candidate: template std::_Expr, typename std::__fun::result_type> std::operator-(const std::valarray<_Tp>&, const std::valarray<_Tp>&) _DEFINE_BINARY_OPERATOR(-, __minus) ^ /usr/include/c++/7/valarray:1173:1: note: template argument deduction/substitution failed: main.cpp:25:19: note: mismatched types 'const std::valarray<_Tp>' and 'int' a[i]=l-a[i]; ^ In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95:0, from main.cpp:1: /usr/include/c++/7/valarray:1173:1: note: candidate: template std::_Expr, typename std::__fun::result_type> std::operator-(const std::valarray<_Tp>&, const _Tp&) _DEFINE_BINARY_OPERATOR(-, __minus) ^ /usr/include/c++/7/valarray:1173:1: note: template argument deduction/substitution failed: main.cpp:25:19: note: mismatched types 'const std::valarray<_Tp>' and 'int' a[i]=l-a[i]; ^ In file included from /usr/include/x86_64-linux-gnu/c++/7/bits/stdc++.h:95:0, from main.cpp:1: /usr/include/c++/7/valarray:1173:1: note: candidate: template std::_Expr, typename std::__fun::result_type> std::operator-(const _Tp&, const std::valarray<_Tp>&) _DEFINE_BINARY_OPERATOR(-, __minus) ^ /usr/include/c++/7/valarray:1173:1: note: template argument deduction/substitution failed: main.cpp:25:19: note: 'car' is not derived from 'const std::valarray<_Tp>' a[i]=l-a[i]; ^