Eroare de compilare: user.cpp: In function ‘int main()’: user.cpp:23:18: error: no match for ‘operator-’ (operand types are ‘std::string {aka std::basic_string<char>}’ and ‘char’) int v = n-'0'; ^ user.cpp:23:18: note: candidates are: In file included from /usr/include/c++/4.8/bits/stl_algobase.h:67:0, from /usr/include/c++/4.8/bits/char_traits.h:39, from /usr/include/c++/4.8/ios:40, from /usr/include/c++/4.8/istream:38, from /usr/include/c++/4.8/fstream:38, from user.cpp:1: /usr/include/c++/4.8/bits/stl_iterator.h:327:5: note: template<class _Iterator> typename std::reverse_iterator<_Iterator>::difference_type std::operator-(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&) operator-(const reverse_iterator<_Iterator>& __x, ^ /usr/include/c++/4.8/bits/stl_iterator.h:327:5: note: template argument deduction/substitution failed: user.cpp:23:19: note: ‘std::string {aka std::basic_string<char>}’ is not derived from ‘const std::reverse_iterator<_Iterator>’ int v = n-'0'; ^ In file included from /usr/include/c++/4.8/bits/stl_algobase.h:67:0, from /usr/include/c++/4.8/bits/char_traits.h:39, from /usr/include/c++/4.8/ios:40, from /usr/include/c++/4.8/istream:38, from /usr/include/c++/4.8/fstream:38, from user.cpp:1: /usr/include/c++/4.8/bits/stl_iterator.h:379:5: note: template<class _IteratorL, class _IteratorR> 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++/4.8/bits/stl_iterator.h:379:5: note: template argument deduction/substitution failed: user.cpp:23:19: note: ‘std::string {aka std::basic_string<char>}’ is not derived from ‘const std::reverse_iterator<_Iterator>’ int v = n-'0'; ^ In file included from /usr/include/c++/4.8/bits/stl_algobase.h:67:0, from /usr/include/c++/4.8/bits/char_traits.h:39, from /usr/include/c++/4.8/ios:40, from /usr/include/c++/4.8/istream:38, from /usr/include/c++/4.8/fstream:38, from user.cpp:1: /usr/include/c++/4.8/bits/stl_iterator.h:1104:5: note: template<class _IteratorL, class _IteratorR> decltype ((__x.base() - __y.base())) std::operator-(const std::move_iterator<_Iterator>&, const std::move_iterator<_IteratorR>&) operator-(const move_iterator<_IteratorL>& __x, ^ /usr/include/c++/4.8/bits/stl_iterator.h:1104:5: note: template argument deduction/substitution failed: user.cpp:23:19: note: ‘std::string {aka std::basic_string<char>}’ is not derived from ‘const std::move_iterator<_Iterator>’ int v = n-'0'; ^ In file included from /usr/include/c++/4.8/bits/stl_algobase.h:67:0, from /usr/include/c++/4.8/bits/char_traits.h:39, from /usr/include/c++/4.8/ios:40, from /usr/include/c++/4.8/istream:38, from /usr/include/c++/4.8/fstream:38, from user.cpp:1: