From: Mark Hubbart <discord@...>
Date: 2004-07-18T09:04:05+09:00
Subject: Re: [NUBY] Ruby Way code for shuffling an array doesn't behave as expected


On Jul 17, 2004, at 4:12 PM, Alexey Verkhovsky wrote:

> On Sun, 2004-07-18 at 01:43, Mark Sparshatt wrote:
>> It's because the block passed to collect is changing the contents of 
>> a,
>> so it doesn't reach all the elements of a.
>
> So, Ruby iterators operate on the original collection and let you 
> modify
> the collection in the process. Another fact useful to remember.
>
> This is, by the way, one thing I like about Java iterators: they are
> fail-safe in such scenarios. E.g.
>
> List list = new ArrayList(2);
> list.add(new Object());
> list.add(new Object());
> Iterator i = list.iterator();
> i.next(); // this is OK
> list.add(new Object()); // list gets changed
> i.next(); // throws ConcurrentModificationException
>
> IMHO, an exception here is The Right Thing (TM). At least, it saved me
> from my own stupid mistakes more than once.

I'm not sure that an exception would be The Right Thing, but I do 
wonder why it no longer works on a copy of the array? Allowing 
modification of the actual array as you iterate over it seems 
dangerous.

But there must have been a reason for abandoning the original 
behavior... Perhaps it was a performance issue?

cheers,
Mark