RFC on range design for D2

[Fawzi Mohamed]

I like the new proposal much more than the first.

I believe you will be able to use it successfully in std.algorithm.
I still would have preferred an operation like a sameHead or 
compareHeadPosition (that might or might not return the order, but at 
least tests for equality) so that upon request (-debug flag?) one would 
be able to make all range operation safe (with overhead) in a generic 
way, but it is up to you.

I what I really care about is the following:
I want foreach magic on all objects that support .done and .next, even 
if they are not ranges.
foreach is about iteration, iteration needs only .done and .next (a 
generator, iterator whatever), and it should work with that.
Do not force the range idea on foreach iteration.
foreach is a language construct, not a library one and should allow for 
maximum flexibility.

As extra nicety as each generator/iterator/range returns just one 
object I would like to be able to do:

// i counts starting from 1, j iterates on iterJ and in parallel k 
iterates on a.all
foreach(i,j,k;1..$,iterJ,a.all){
	//...
}

and have it expanded to

Range!(int) r1=1..$;
alias iterJ r2;
typeof(a.all) r3=a.all;
while(!(r1.done || r2.done || r3.done)){
	typeof(r1.next) i=r1.next;
	typeof(r2.next) j=r2.next;
	typeof(r3.next) k=r3.next;
	//...
}

Fawzi