operator==,!=,<,<=,>,>=(std::experimental::observer_ptr)

From cppreference.com
template<class W1, class W2>
bool operator==(const observer_ptr<W1>& p1, const observer_ptr<W2>& p2);
(1) (library fundamentals TS v2)
template<class W1, class W2>
bool operator!=(const observer_ptr<W1>& p1, const observer_ptr<W2>& p2);
(2) (library fundamentals TS v2)
template<class W>
bool operator==(const observer_ptr<W>& p, std::nullptr_t);
(3) (library fundamentals TS v2)
template<class W>
bool operator==(std::nullptr_t, const observer_ptr<W>& p);
(4) (library fundamentals TS v2)
template<class W>
bool operator!=(const observer_ptr<W>& p, std::nullptr_t);
(5) (library fundamentals TS v2)
template<class W>
bool operator!=(std::nullptr_t, const observer_ptr<W>& p);
(6) (library fundamentals TS v2)
template<class W1, class W2>
bool operator<(const observer_ptr<W1>& p1, const observer_ptr<W2>& p2);
(7) (library fundamentals TS v2)
template<class W1, class W2>
bool operator>(const observer_ptr<W1>& p1, const observer_ptr<W2>& p2);
(8) (library fundamentals TS v2)
template<class W1, class W2>
bool operator<=(const observer_ptr<W1>& p1, const observer_ptr<W2>& p2);
(9) (library fundamentals TS v2)
template<class W1, class W2>
bool operator>=(const observer_ptr<W1>& p1, const observer_ptr<W2>& p2);
(10) (library fundamentals TS v2)

Compares the pointer values of two observer_ptrs, or a observer_ptr and nullptr.

1-2) Equality comparison for two observer_ptrs
3-6) Equality comparison for an observer_ptr and nullptr.
7-10) Ordered comparison for two observer_ptrs

[edit] Parameters

p, p1, p2 - observer_ptrs to compare

[edit] Return value

1) p1.get() == p2.get()

2) !(p1 == p2)

3-4) !p

5-6) (bool)p

7) std::less<W3>()(p1.get(), p2.get()), where W3 is the composite pointer type of W1* and W2*

8) p2 < p1

9) !(p2 < p1)

10) !(p1 < p2)

[edit] Exceptions

3-6)
noexcept specification:  
noexcept