Hi Dan,
On lundi 13 juin 2022 19:49:10 CEST Dan Ackroyd wrote:
> > Auto-capture in PHP is by-value. This makes this impossible. It also makes
> > explicit declarations non-necessary and much less useful.
>
> Separating off some pedantism from the hopefully constructive comment,
>
> I think some of the words in the RFC are a bit inaccurate:
> > A by-value capture means that it is not possible to modify any variables
> > from the outer scope:
> >
> > Because variables are bound by-value, the confusing behaviors often
> > associated with closures do not exist.
> >
> > Because variables are captured by-value, Short Closures can not have
> > unintended side effects.
> Those statements are true for scalar values. They are not true for objects:
This is shown in the "No unintended side-effects" section of the RFC.
I agree that the choice of words is inaccurate, as "modify any variable" could
be interpreted not only as "bind a variable", but also as "mutate a value".
The section you have quoted is meant to show how by-value capture, which is
the default capture mode in all PHP closures, is less error prone than by-
variable/by-reference capture, by a huge margin. Especially since variable
bindings do not have side-effects unless a variable was explicitly captured
by-reference. Do you agree with this ?
The "No unintended side-effects" section assumes that property assignments to
captured variables are intended side-effects. In your example, the programmer
intended to have a side effect because `$a` can only come from the declaring
scope (the code would result in an error otherwise) :
> $a = new Foo('bar');
> $f = fn() {
> $a->value = 'explicit scope is nice';
> };
Do you have an example where the intent would be less obvious ? With code you
would actually write ?
Cheers,
--
Arnaud Le Blanc
--
PHP Internals - PHP Runtime Development Mailing List
To unsubscribe, visit: https://www.php.net/unsub.php
