about const iterators

[masterinex]

can anyone tell me what the difference btw the iterator

const_reverse_iterator rbegin()

and const_reverse_iterator crbegin() ?

How should i write BOOST unit test case for each scenario?

 
in a header file i have the following definition for 
iterators: 


// iterators
	iterator begin() noexcept { return iterator(beg_); }
	iterator end() noexcept { return iterator(end_); }
	const_iterator cbegin() const noexcept { return const_iterator(beg_); }
	const_iterator cend() const noexcept { return const_iterator(end_); }
	const_iterator begin() const noexcept { return cbegin(); }
	const_iterator end() const noexcept { return cend(); }

	reverse_iterator rbegin() noexcept { return reverse_iterator(end_); }
	reverse_iterator rend() noexcept { return reverse_iterator(beg_); }
	const_reverse_iterator crbegin() const noexcept { return const_reverse_iterator(end_); }
	const_reverse_iterator crend() const noexcept { return const_reverse_iterator(beg_); }
	const_reverse_iterator rbegin() const noexcept { return cbegin(); }
	const_reverse_iterator rend() const noexcept { return cend(); }

[JLBorges]

const_reverse_iterator crbegin() const returns a const iterator even if the sequence container is non-const.

This is a bug:

const_reverse_iterator rbegin() const noexcept { return cbegin(); }
const_reverse_iterator rend() const noexcept { return cend(); }

Once it is corrected,

const_reverse_iterator rbegin() const noexcept { return crbegin(); }
const_reverse_iterator rend() const noexcept { return crend(); }

we would need to write test cases only for one of these pairs:
either a. cbegin() and cend() or b. begin() and end() on a const sequence container.

If it is a class room exercise, and the code compiles cleanly, this bug may have been deliberately introduced, to test if you can catch it with a test case. You need to test that reverse iterators iterate in the reverse direction.