From: Roshan James <roshanj@...>
Date: 2005-03-11T15:57:08+09:00
Subject: Re: Is iterating in lock-step possible?

Thanks for all the mails. Like William called out, this did not solve
the underlying problem. 

<Repeat>
In my post, I chose the array.each only as an example. Its not arrays
for which I want to do this with - I want to solve the problem for
iterator calls. If zip() internally creates a list of values from both
iterations, then it does not help me. I want to be able to do the actual
computation of the iterator calls in lock-step.
</Repeat>

I was trying to write code where I can have two or more computations
which generate values that I need to compare - with the ruby syntax
tying iterator usage to the code blocks by syntax, there is no way I can
do this. This is especially applicable when the iterators potentially
return an infinite stream of values. (Except for using contiuations...
Which is not really so much of a solution, because I might as well not
have used an iterator in a first place if I could create good
coroutines)

Yes I understand that I take a hit (wrt perf by choosing ruby), but
that's a BAD argument to favour wrapping state first by a iterators and
then once over by a continuation. 

On a related note, I had asked this question about C# and it looks like
C# can do both of these cleanly - 
foreach(<type> t in foo())
{
	foreach(<type> t in bar())
	{
		//nested
	}
}

And - 

IEnumerator<int> ie1 = a.foo().GetEnumerator();
IEnumerator<int> ie2 = a.bar().GetEnumerator();

while (ie1.MoveNext() && ie2.MoveNext())
{
	//lockstep
}


Since Ruby is open to (I believe) a major language redesign these days,
this might be a good feature to consider adding. 


Roshan