Implementing custom iterator to work with std::find - c++

Question

I'm trying to implement a custom doubly linked list which works with std::find and other algorithms, I made a iterator for it which works with for loop however it does not work and is giving me a lot of errors, where do you think my problem is?
here is my simplified code:
template<typename T, class Allocator = std::allocator<T>>
class MyList {
private:
class Link {
public:
T item;
std::shared_ptr<Link> next; // next item
std::shared_ptr<Link> prev; // previous item
};
std::shared_ptr<Link> head;
std::shared_ptr<Link> tail;
public:
using allocator_type = Allocator;
using reference_link = T &;
class iterator {
public:
typedef iterator self_type;
typedef Link value_type;
typedef Link &reference;
typedef std::shared_ptr<Link> pointer;
typedef std::forward_iterator_tag iterator_category;
typedef int difference_type;
iterator(pointer ptr) : _link(ptr) { }
self_type operator++() {
std::shared_ptr<Link> temp{new Link};
if (_link->next) {
temp->item = _link->next->item;
temp->next = _link->next->next;
temp->prev = _link->next->prev;
}
else {
temp->next = nullptr;
temp->prev = _link->prev->next;
}
this->_link = temp;
return *this;
}
self_type operator++(int junk) {
std::shared_ptr<Link> temp{new Link};
if (_link->next) {
temp->item = _link->next->item;
temp->next = _link->next->next;
temp->prev = _link->next->prev;
}
else {
temp->next = nullptr;
temp->prev = _link->prev->next;
}
this->_link = temp;
return *this;
}
reference operator*() { return *_link; }
pointer operator->() { return _link; }
bool operator==(const self_type &l) const {
if (_link->next == l._link->next && _link->prev == l._link->prev && _link->item == l._link->item) {
return true;
}
return false;
}
bool operator!=(const self_type &l) const {
return !operator==(l);
}
friend bool operator==(const iterator &lhs, const T &rhs) {
if (lhs->item == rhs) {
return true;
}
return false;
};
private:
pointer _link;
};
iterator begin();
iterator end();
using iterator = iterator;
using const_iterator = const iterator;
};
template<typename T, class Allocator>
typename MyList<T, Allocator>::iterator MyList<T, Allocator>::begin() {
return iterator{tail};
}
template<typename T, class Allocator>
typename MyList<T, Allocator>::iterator MyList<T, Allocator>::end() {
return (iterator{head})++;
}
This one works fine:
MyList<int, std::allocator<int>> m_list{1, 2, 3,};
for (MyList<int, std::allocator<int>>::iterator i = m_list.begin();
i != m_list.end(); ++i) {
std::cout << i->item;
}
but this gives me many error:
auto result1 = std::find(m_list.begin(), m_list.end(), 3 );
Which some are these:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h: In instantiation of ‘_InputIterator std::__find(_InputIterator, _InputIterator, const _Tp&, std::input_iterator_tag) [with _InputIterator = MyList<int, std::allocator<int> >::iterator; _Tp = int]’:
/usr/include/c++/4.8/bits/stl_algo.h:4441:45: required from ‘_IIter std::find(_IIter, _IIter, const _Tp&) [with _IIter = MyList<int, std::allocator<int> >::iterator; _Tp = int]’
/home/epezhman/cpp/Part1/assignment4/src/main.cpp:44:63: required from here
/usr/include/c++/4.8/bits/stl_algo.h:139:46: error: no match for ‘operator==’ (operand types are ‘MyList<int, std::allocator<int> >::Link’ and ‘const int’)
while (__first != __last && !(*__first == __val))
^
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: candidates are:
In file included from /usr/include/c++/4.8/random:52:0,
from /usr/include/c++/4.8/bits/stl_algo.h:65,
from /usr/include/c++/4.8/algorithm:62,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/random.tcc:2030:5: note: template<class _RealType1> bool std::operator==(const std::normal_distribution<_RealType>&, const std::normal_distribution<_RealType>&)
operator==(const std::normal_distribution<_RealType>& __d1,
^
/usr/include/c++/4.8/bits/random.tcc:2030:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: ‘MyList<int, std::allocator<int> >::Link’ is not derived from ‘const std::normal_distribution<_RealType>’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/vector:64:0,
from /usr/include/c++/4.8/bits/random.h:34,
from /usr/include/c++/4.8/random:50,
from /usr/include/c++/4.8/bits/stl_algo.h:65,
from /usr/include/c++/4.8/algorithm:62,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_vector.h:1404:5: note: template<class _Tp, class _Alloc> bool std::operator==(const std::vector<_Tp, _Alloc>&, const std::vector<_Tp, _Alloc>&)
operator==(const vector<_Tp, _Alloc>& __x, const vector<_Tp, _Alloc>& __y)
^
/usr/include/c++/4.8/bits/stl_vector.h:1404:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: ‘MyList<int, std::allocator<int> >::Link’ is not derived from ‘const std::vector<_Tp, _Alloc>’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/iterator:66:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:4,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stream_iterator.h:130:5: note: template<class _Tp, class _CharT, class _Traits, class _Dist> bool std::operator==(const std::istream_iterator<_Tp, _CharT, _Traits, _Dist>&, const std::istream_iterator<_Tp, _CharT, _Traits, _Dist>&)
operator==(const istream_iterator<_Tp, _CharT, _Traits, _Dist>& __x,
^
/usr/include/c++/4.8/bits/stream_iterator.h:130:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: ‘MyList<int, std::allocator<int> >::Link’ is not derived from ‘const std::istream_iterator<_Tp, _CharT, _Traits, _Dist>’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/bits/locale_facets.h:48:0,
from /usr/include/c++/4.8/bits/basic_ios.h:37,
from /usr/include/c++/4.8/ios:44,
from /usr/include/c++/4.8/ostream:38,
from /usr/include/c++/4.8/iostream:39,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:2,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/streambuf_iterator.h:204:5: note: template<class _CharT, class _Traits> bool std::operator==(const std::istreambuf_iterator<_CharT, _Traits>&, const std::istreambuf_iterator<_CharT, _Traits>&)
operator==(const istreambuf_iterator<_CharT, _Traits>& __a,
^
/usr/include/c++/4.8/bits/streambuf_iterator.h:204:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: ‘MyList<int, std::allocator<int> >::Link’ is not derived from ‘const std::istreambuf_iterator<_CharT, _Traits>’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/memory:82:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:1,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/shared_ptr.h:338:5: note: template<class _Tp> bool std::operator==(std::nullptr_t, const std::shared_ptr<_Tp1>&)
operator==(nullptr_t, const shared_ptr<_Tp>& __a) noexcept
^
/usr/include/c++/4.8/bits/shared_ptr.h:338:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: cannot convert ‘__first.MyList<T, Allocator>::iterator::operator*<int, std::allocator<int> >()’ (type ‘MyList<int, std::allocator<int> >::Link’) to type ‘std::nullptr_t’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/memory:82:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:1,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/shared_ptr.h:333:5: note: template<class _Tp> bool std::operator==(const std::shared_ptr<_Tp1>&, std::nullptr_t)
operator==(const shared_ptr<_Tp>& __a, nullptr_t) noexcept
^
/usr/include/c++/4.8/bits/shared_ptr.h:333:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: ‘MyList<int, std::allocator<int> >::Link’ is not derived from ‘const std::shared_ptr<_Tp1>’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/memory:82:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:1,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/shared_ptr.h:327:5: note: template<class _Tp1, class _Tp2> bool std::operator==(const std::shared_ptr<_Tp1>&, const std::shared_ptr<_Tp2>&)
operator==(const shared_ptr<_Tp1>& __a,
^
/usr/include/c++/4.8/bits/shared_ptr.h:327:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: ‘MyList<int, std::allocator<int> >::Link’ is not derived from ‘const std::shared_ptr<_Tp1>’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/bits/shared_ptr.h:52:0,
from /usr/include/c++/4.8/memory:82,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:1,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/shared_ptr_base.h:1040:5: note: template<class _Tp, __gnu_cxx::_Lock_policy _Lp> bool std::operator==(std::nullptr_t, const std::__shared_ptr<_Tp, _Lp>&)
operator==(nullptr_t, const __shared_ptr<_Tp, _Lp>& __a) noexcept
^
/usr/include/c++/4.8/bits/shared_ptr_base.h:1040:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: cannot convert ‘__first.MyList<T, Allocator>::iterator::operator*<int, std::allocator<int> >()’ (type ‘MyList<int, std::allocator<int> >::Link’) to type ‘std::nullptr_t’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/bits/shared_ptr.h:52:0,
from /usr/include/c++/4.8/memory:82,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:1,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/shared_ptr_base.h:1035:5: note: template<class _Tp, __gnu_cxx::_Lock_policy _Lp> bool std::operator==(const std::__shared_ptr<_Tp, _Lp>&, std::nullptr_t)
operator==(const __shared_ptr<_Tp, _Lp>& __a, nullptr_t) noexcept
^
/usr/include/c++/4.8/bits/shared_ptr_base.h:1035:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: ‘MyList<int, std::allocator<int> >::Link’ is not derived from ‘const std::__shared_ptr<_Tp, _Lp>’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/bits/shared_ptr.h:52:0,
from /usr/include/c++/4.8/memory:82,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:1,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/shared_ptr_base.h:1029:5: note: template<class _Tp1, class _Tp2, __gnu_cxx::_Lock_policy _Lp> bool std::operator==(const std::__shared_ptr<_Tp1, _Lp>&, const std::__shared_ptr<_Tp2, _Lp>&)
operator==(const __shared_ptr<_Tp1, _Lp>& __a,
^
/usr/include/c++/4.8/bits/shared_ptr_base.h:1029:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: ‘MyList<int, std::allocator<int> >::Link’ is not derived from ‘const std::__shared_ptr<_Tp1, _Lp>’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/memory:81:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:1,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/unique_ptr.h:500:5: note: template<class _Tp, class _Dp> bool std::operator==(std::nullptr_t, const std::unique_ptr<_Tp, _Dp>&)
operator==(nullptr_t, const unique_ptr<_Tp, _Dp>& __x) noexcept
^
/usr/include/c++/4.8/bits/unique_ptr.h:500:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: cannot convert ‘__first.MyList<T, Allocator>::iterator::operator*<int, std::allocator<int> >()’ (type ‘MyList<int, std::allocator<int> >::Link’) to type ‘std::nullptr_t’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/memory:81:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:1,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/unique_ptr.h:495:5: note: template<class _Tp, class _Dp> bool std::operator==(const std::unique_ptr<_Tp, _Dp>&, std::nullptr_t)
operator==(const unique_ptr<_Tp, _Dp>& __x, nullptr_t) noexcept
^
/usr/include/c++/4.8/bits/unique_ptr.h:495:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: ‘MyList<int, std::allocator<int> >::Link’ is not derived from ‘const std::unique_ptr<_Tp, _Dp>’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/memory:81:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:1,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/unique_ptr.h:489:5: note: template<class _Tp, class _Dp, class _Up, class _Ep> bool std::operator==(const std::unique_ptr<_Tp, _Dp>&, const std::unique_ptr<_Up, _Ep>&)
operator==(const unique_ptr<_Tp, _Dp>& __x,
^
/usr/include/c++/4.8/bits/unique_ptr.h:489:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: ‘MyList<int, std::allocator<int> >::Link’ is not derived from ‘const std::unique_ptr<_Tp, _Dp>’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/memory:79:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:1,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/functional:2543:5: note: template<class _Res, class ... _Args> bool std::operator==(std::nullptr_t, const std::function<_Res(_ArgTypes ...)>&)
operator==(nullptr_t, const function<_Res(_Args...)>& __f) noexcept
^
/usr/include/c++/4.8/functional:2543:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: cannot convert ‘__first.MyList<T, Allocator>::iterator::operator*<int, std::allocator<int> >()’ (type ‘MyList<int, std::allocator<int> >::Link’) to type ‘std::nullptr_t’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/memory:79:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:1,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/functional:2537:5: note: template<class _Res, class ... _Args> bool std::operator==(const std::function<_Res(_ArgTypes ...)>&, std::nullptr_t)
operator==(const function<_Res(_Args...)>& __f, nullptr_t) noexcept
^
/usr/include/c++/4.8/functional:2537:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: ‘MyList<int, std::allocator<int> >::Link’ is not derived from ‘const std::function<_Res(_ArgTypes ...)>’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/functional:55:0,
from /usr/include/c++/4.8/memory:79,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:1,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/tuple:813:5: note: template<class ... _TElements, class ... _UElements> constexpr bool std::operator==(const std::tuple<_Elements ...>&, const std::tuple<_Elements ...>&)
operator==(const tuple<_TElements...>& __t,
^
/usr/include/c++/4.8/tuple:813:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: ‘MyList<int, std::allocator<int> >::Link’ is not derived from ‘const std::tuple<_Elements ...>’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/tuple:39:0,
from /usr/include/c++/4.8/functional:55,
from /usr/include/c++/4.8/memory:79,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:1,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/array:228:5: note: template<class _Tp, long unsigned int _Nm> bool std::operator==(const std::array<_Tp, _Nm>&, const std::array<_Tp, _Nm>&)
operator==(const array<_Tp, _Nm>& __one, const array<_Tp, _Nm>& __two)
^
/usr/include/c++/4.8/array:228:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: ‘MyList<int, std::allocator<int> >::Link’ is not derived from ‘const std::array<_Tp, _Nm>’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/string:52:0,
from /usr/include/c++/4.8/stdexcept:39,
from /usr/include/c++/4.8/array:38,
from /usr/include/c++/4.8/tuple:39,
from /usr/include/c++/4.8/functional:55,
from /usr/include/c++/4.8/memory:79,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:1,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/basic_string.h:2519:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const std::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*)
operator==(const basic_string<_CharT, _Traits, _Alloc>& __lhs,
^
/usr/include/c++/4.8/bits/basic_string.h:2519:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: ‘MyList<int, std::allocator<int> >::Link’ is not derived from ‘const std::basic_string<_CharT, _Traits, _Alloc>’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/string:52:0,
from /usr/include/c++/4.8/stdexcept:39,
from /usr/include/c++/4.8/array:38,
from /usr/include/c++/4.8/tuple:39,
from /usr/include/c++/4.8/functional:55,
from /usr/include/c++/4.8/memory:79,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:1,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/basic_string.h:2507:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator==(const _CharT*, const std::basic_string<_CharT, _Traits, _Alloc>&)
operator==(const _CharT* __lhs,
^
/usr/include/c++/4.8/bits/basic_string.h:2507:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: mismatched types ‘const _CharT*’ and ‘MyList<int, std::allocator<int> >::Link’
while (__first != __last && !(*__first == __val))
^
In file included from /usr/include/c++/4.8/string:52:0,
from /usr/include/c++/4.8/stdexcept:39,
from /usr/include/c++/4.8/array:38,
from /usr/include/c++/4.8/tuple:39,
from /usr/include/c++/4.8/functional:55,
from /usr/include/c++/4.8/memory:79,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:1,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/basic_string.h:2493:5: note: template<class _CharT> typename __gnu_cxx::__enable_if<std::__is_char<_Tp>::__value, bool>::__type std::operator==(const std::basic_string<_CharT>&, const std::basic_string<_CharT>&)
operator==(const basic_string<_CharT>& __lhs,
^
/usr/include/c++/4.8/bits/basic_string.h:2493:5: note: template argument deduction/substitution failed:
In file included from /usr/include/c++/4.8/algorithm:62:0,
from /home/epezhman/cpp/Part1/assignment4/exercise_1/include/my_list.h:5,
from /home/epezhman/cpp/Part1/assignment4/src/main.cpp:1:
/usr/include/c++/4.8/bits/stl_algo.h:139:46: note: ‘MyList<int, std::allocator<int> >::Link’ is not derived from ‘const std::basic_string<_CharT>’
while (__first != __last && !(*__first == __val))

Answer 1

It looks like your value_type and reference should use T not Link. (You want to iterate over the values, not the links containing them.) operator * and operator -> need to change appropriately.