[Gecode] Improved integer domain representation

[Christian Schulte]

Dear all,

I improved the representation of integer domains. They are now implenmented
using a bidirectional list. This gives the following complexity:

	<=, >=			O(n) and O(1) amortized
	!=, ==			O(n)
	narrow			O(m) (where m is number of ranges for
iterator argument)
	inter, minus		O(n+m)

In addition, for != and == the number of iterations performed is n/2 (in
average).

As you have seen I also have renamed the domain operations involving range
iterators:
	narrow(Iterator& i)	replaces the current domain of the variable
with the ranges as defined by i,
					the ranges for I must define a
subset of the current domain
	inter(Iterator& i)	intersection of current domain with I
	minus(Iterator& i)	remove ranges from current domain as defined
by I

What still needs to be done is to make the iterators take advantage of the
biderectional representation of integer domains. But I think I will not have
any time in the short fututure.

Cheers
Christian
 
-- 
Christian Schulte, http://www.imit.kth.se/~schulte/