icmp - should this go in itertools?

[Tom Anderson]

On Sat, 26 Nov 2005, Diez B. Roggisch wrote:

> Tom Anderson wrote:
>
>> Is this any good? Would it be any use? Should this be added to itertools?
>
> Whilst not a total itertools-expert myself, I have one little objection 
> with this: the comparison won't let me know how many items have been 
> consumed. And I end up with two streams that lack some common prefix 
> plus one field.

Good point. It would probably only be useful if you didn't need to do 
anything with the iterators afterwards.

One option - which is somewhat icky - would be to encode that in the 
return value; if n is the number of items read from both iterators, then 
if the first argument is smaller, the return value is -n, and if the 
second is smaller, it's n. The trouble is that you couldn't be sure 
exactly how many items had been read from the larger iterator - it could 
be n, if the values in the iterators differ, or n+1, if the values were 
the same but the larger one was longer.

> I'm just not sure if there is any usecase for that.

I used it in my ordered dictionary implementation; it was a way of 
comparing two 'virtual' lists that are lazily generated on demand.

I'll go away and think about this more.

tom

-- 
Gotta treat 'em mean to make 'em scream.