Initial version of express method now works.\
	Yay!
Express method is finally working.
	After a lot of unrelated errors, the express method is
	finally working. There are some hacks - I have added a TODO
	wherever I felt something more could be done; this has also
	been done in the case of hacks. The flatten method is one
	major cause of implementing hacks - I have mentioned that
	many times in the code.
	The results obtained are mathematically correct but they
	aren't simplified. For that, I'll need to write custom
	simplify methods - which shouldn't take long.