Re: Re: [PHP-DEV] [RFC] Generators

On 2012-08-23 00:10, Lester Caine wrote:

Then the next example is an 'iterator' ... which you are right ... I do not appreciate either, because they require an insane amount of overhead for what would be easy if the first example had been done right! I did try them, in the past, but the overhead outweighed any advantage and I can't find them in any of the projects I work with apart as a blank frame in ADOdb ... which nobody seems to use. But as far as I've been able to make out, your method _still_ has the overhead of maintaining state during the iteration - only now it's each consumer's responsibility to remember its state between successive notifications by the producer. The producer can't help with that, because each consumer has different maintenance requirements; managing the iteration process has therefore been split across two distinct objects with the consumer doing the hard part (which is why the producer looks so simple).

I suppose if you're lucky the consumer doesn't need to remember any state between one notification and the next, and it can treat every dataum like it's the first. But that is hardly the general case. To describe iterators further, here are a few links (note that they're not necessarily the best - they're just the first non-Wikipedia, non-Amazon links I got when Googling for "Design Patterns"): http://www.dofactory.com/Patterns/PatternIterator.aspx http://www.oodesign.com/iterator-pattern.html http://sourcemaking.com/design_patterns/iterator It might also help to compare the Observer pattern, in the special case where the one-many relationship is actually one-one.