On 02/08/2016 09:56, Christoph Becker wrote:
For the record: there has been the "Array Of" RFC[1], but that has been
declined.
[1] <https://wiki.php.net/rfc/arrayof>
If I remember rightly, the biggest problem raised with typed arrays is
that type constraints in PHP are checked dynamically every time a
function is called, so the cost of iterating the array to test its type
can be rather costly:
function foo(Thing[] $things) { }
$data = array_fill(0, 10000000, new Thing);
foo($data); // performs 10000000 instanceof checks
foo($data); // performs another 10000000 instanceof checks
$data[] = new NotAThing;
foo($data); // will throw error only after 10000001 instanceof checks
# TOTAL: 30000001 instanceof checks
This is not the same with generics, because the container itself
performs the check, as items are added:
function foo(TypedArray<Thing> $things) { }
$data = new TypedArray<Thing>;
foreach ( array_fill(0, 10000000, new Thing) as $thing ) {
$data->add($thing); // 10000000 instanceof checks here
}
foo($data); // performs one instanceof check on the container
foo($data); // performs one instanceof check on the container
$data->add(new NotAThing); // performs 1 instanceof check and errors
# TOTAL: 10000003 instanceof checks
In this trivial example, you could replace the foreach loop with
something like $data->fill(0, 10000000, new Thing) and reduce the whole
thing to 4 instanceof checks. There is no equivalent shortcut for the
Thing[] version.
This is a fundamental problem with PHP's type constraints - because they
are not attached to the value itself, they act as assertions that must
be executed repeatedly. The more complex we make them, and the more
places they're added, the more this becomes a limiting factor.
Regards,
--
Rowan Collins
[IMSoP]
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