Dan Ackroyd wrote: > This looks to solve a problem very similar to the one solved by the > 'Memoize' annotation in HHVM - > https://docs.hhvm.com/hack/attributes/special#__memoize
> However the memoize functionality seems a lot clearer to me, as it's > less 'magic'; it doesn't make accessing a variable actually call a > function. On really it seems a very good feature focused on method call. Maybe it can be done in same idea, by freezing the first result of method. But I think hard do that with args. Maybe something like that: http://pastebin.com/YKjEYeYF Note: I know that is better an IoC, understand just as example. Dan Ackroyd wrote: > This code has a circular dependency: > > class Foo { > public $a, $b; > public __construct() { > $this->a = lazy { return 1 + $this->b; } > $this->b = lazy { return 1 + $this->a; } > } > } > > $foo = new Foo; > echo $foo->a; > > $foo->a can't be resolved until $foo->b is resolved, and $foo->b can't > be resolved until $foo->a is resolved. Now back to topic, this circular dependency too occur with functions. Basically if it happen, should throw a infinite recursion error. (Currently I guess that PHP don't do that, but xdebug does) In all case, $a should not depends of $b, when $b depends $a. In this case, should have a bootstrap system, that turn it independent. Example: class Foo { public $a, $b; public __construct () { $c = lazy { return generalDependency(); } $this->a = lazy use ($c) { return 1 + $c; }; $this->b = lazy use ($c) { return 1 + $c; }; } } Dan Ackroyd wrote: > Because the 'memoization' of functions is less magic, it is much less > prone to this circular dependency problem. I guess that memoization is another topic, but still very interesting, as cited above. So maybe it can be discussed apart of this email, if is reasonable. Stanislav Malyshev wrote: > > This Feature Request is about the implementation of lazy statements. > > > > Basically it should implements a 'lazy' keyword (or similar) and > > structured like an anonymous function, except that it doesn't accepts > > arguments, but accept the use() feature. > > > > $var = lazy { return 1; } > > Is this just keystroke saving for function() or is this supposed to do > something additional? It's similar to function (), but should be applied to variables or properties only. But exists an important difference between you use lazy vs function (). $var1 = function () { sleep(5); return 1; } $var2 = lazy { sleep(5); return 1; } - $var1 should be called like $var1(); - If I call $var1() five times, it'll execute this structure over 25 seconds; - If I try to write over $var1(), possible I should get an error trying to write over int (1); - $var2 should be called like $var2 directly; - If I call $var2 five times, it'll execute once the structure, custing 5 seconds only; - If I try to write over $var2 it'll, in fact, write over $var2 processed structure, that stores int (1); -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
