Hi! > It's not that you can't make an array into a generator, but you can't make > an eagerly-evaluated expression into a lazily-evaluated one.
Not sure what you mean here. If you already have the data, of course you can't un-evaluate it in order to lazily-evaluate it again. But why would you, that would be just a waste of time! If you don't yet have the data, then you usually can easily rewrite the code that produces it as a generator if you wanted, but in most cases you don't need it as it would be more complex and won't give you any advantage (exceptions of course exist like processing enormous files or processing infinite streams continuously). So I am not seeing the point of mentioning "eager to lazy" case as it is usually does not happen in practice. > $hugeCSVFileIterator = new CSVFileLazyLoader($filename); > $filteredCSVFileIterator = [ foreach $hugeCSVFileIterator as $line if > $line['type'] == 'foo' yield $line['value'] ]; In this particular case, when you're working with an iterator over a large file, you probably want a generator. Which is very easy to write using a functional syntax, and the only thing comprehension syntax does is switching the parts around a bit and saving you writing a "function" keyword. I don't think it's a very common case though. > Similarly, an array-only syntax is useless for infinite iterators, whereas > an iterator version lets you write a filtered version that's still infinite. Of course, when you need to filter iterators, then you need a different approach. I do not doubt that. I doubt that filtering iterators is the most common case in PHP to make the comprehension syntax only support it - I think the case of array transformation is much more common. > But if we only have one, it should be the iterator version, with a > short-hand for iterator_to_array as a separate language improvement. I think this would significantly reduce the usability of such construct - to the point that it's easier to use the existing syntax, thus making new syntax sugar useless. The whole point of syntax sugar is making common case easy, and doing what you are suggesting is to make a corner case (existing, but IMHO much less common) easy and make the user work to achieve the common case. -- Stas Malyshev smalys...@gmail.com -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
