[RFC] Allow "use( $longname as $alias)" syntax for closures declaration

13 years ago by Laruence — view source

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Hi:
I have made a RFC to allow user use T_AS in the closure declaration, like:

 function () use($long as $l, &$long as $r) {
 }

 here is the RFC: https://wiki.php.net/rfc/useas

 any ideas?  thanks

--
Laruence Xinchen Hui
http://www.laruence.com/

13 years ago by Matthew Weier O'Phinney — view source

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I have made a RFC to allow user use T_AS in the closure declaration, like:

function () use($long as $l, &$long as $r) {
}

here is the RFC: https://wiki.php.net/rfc/useas

any ideas? thanks

I really like this, as it brings a symmetry to how "use" is used when
importing classes/namespaces; I've often attempted to use "as" within my
closure use statements, only to get burned.

--
Matthew Weier O'Phinney
Project Lead | matthew@zend.com
Zend Framework | http://framework.zend.com/
PGP key: http://framework.zend.com/zf-matthew-pgp-key.asc

13 years ago by Verbitsky Alexander — view source

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Hi:
I have made a RFC to allow user use T_AS in the closure declaration, like:
  function () use($long as $l,&$long as $r) {
  }

  here is the RFC: https://wiki.php.net/rfc/useas

  any ideas?  thanks

Closure is a functional literal that can pull with itself all variables
visible in current scope where it was created. For my opinion using
keyword 'use' is not necessary and i would have removed it. If you need
different name of variable maybe you need anonymous function.

13 years ago by Laruence — view source

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On Fri, Apr 13, 2012 at 4:10 PM, Verbitsky Alexander
verbitsky_alexandr@mail.by wrote:

Hi:
I have made a RFC to allow user use T_AS in the closure declaration,
like:

function () use($long as $l,&$long as $r) {

}

here is the RFC: https://wiki.php.net/rfc/useas

any ideas? thanks

Closure is a functional literal that can pull with itself all variables
visible in current scope where it was created.
Hi:

you mean dup a EG(active_symbol_table)? it's too expensive, IMO.

thanks

For my opinion using keyword
'use' is not necessary and i would have removed it. If you need different
name of variable maybe you need anonymous function.

--

--
Laruence Xinchen Hui
http://www.laruence.com/

13 years ago by Yasuo Ohgaki — view source

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Hi,

2012/4/13 Verbitsky Alexander verbitsky_alexandr@mail.by:

Hi:
I have made a RFC to allow user use T_AS in the closure declaration,
like:

function () use($long as $l,&$long as $r) {

}

here is the RFC: https://wiki.php.net/rfc/useas

any ideas? thanks

Closure is a functional literal that can pull with itself all variables
visible in current scope where it was created. For my opinion using keyword
'use' is not necessary and i would have removed it. If you need different
name of variable maybe you need anonymous function.

You might be used to other language's scoping, but
this is the way PHP works.

Named function cannot do this, but anyway
function FUNC($a, $b, $c) uses ($d, $e, $f) {}
is like
function FUNC($a, $b, $c) { global $d, $e, $f; }

I would rather have this.
function FUNC($a, $b, $c) uses ($d, $e, $f) {}
Then it would be consistent with anonymous function.

There are methods, so we should be careful though.

Regards,

--
Yasuo Ohgaki
yohgaki@ohgaki.net

13 years ago by Charlie Somerville — view source

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I'm at a bit of a loss as to why Laruence is claiming that allowing
closures to implicitly access variables in the outer scope requires
duplicating the symbol table.

Is there any technical reason why it's not possible for scopes to retain a
pointer to their parent scopes so variables can be looked up that way?

Hi,

2012/4/13 Verbitsky Alexander verbitsky_alexandr@mail.by:
Hi:
I have made a RFC to allow user use T_AS in the closure
declaration,
like:
 function () use($long as $l,&$long as $r) {

 }

 here is the RFC: https://wiki.php.net/rfc/useas

 any ideas?  thanks
Closure is a functional literal that can pull with itself all variables
visible in current scope where it was created. For my opinion using
keyword
'use' is not necessary and i would have removed it. If you need different
name of variable maybe you need anonymous function.
You might be used to other language's scoping, but
this is the way PHP works.

Named function cannot do this, but anyway
function FUNC($a, $b, $c) uses ($d, $e, $f) {}
is like
function FUNC($a, $b, $c) { global $d, $e, $f; }

I would rather have this.
function FUNC($a, $b, $c) uses ($d, $e, $f) {}
Then it would be consistent with anonymous function.

There are methods, so we should be careful though.

Regards,

--
Yasuo Ohgaki
yohgaki@ohgaki.net

13 years ago by Stas Malyshev — view source

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Hi!

I'm at a bit of a loss as to why Laruence is claiming that allowing
closures to implicitly access variables in the outer scope requires
duplicating the symbol table.

Because variables need to be stored somewhere after the parent function
exits.

Is there any technical reason why it's not possible for scopes to retain a
pointer to their parent scopes so variables can be looked up that way?

Because the parent scope will be gone by the time closure is called.
Unless we retain a copy of it - which in most cases is very expensive
and impractical - you usually don't need all variables from parent scope

you need 1-2 of them, keeping all of them linked to the closure - and
thus not freed until closure ceases to exist - would be very expensive.
Declaring shared variables explicitly is a trade-off allowing you to not
keep all the variables in case you do not need them.
--
Stanislav Malyshev, Software Architect
SugarCRM: http://www.sugarcrm.com/
(408)454-6900 ext. 227

13 years ago by Verbitsky Alexander — view source

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Hi!

I'm at a bit of a loss as to why Laruence is claiming that allowing
closures to implicitly access variables in the outer scope requires
duplicating the symbol table.
Because variables need to be stored somewhere after the parent function
exits.

Is there any technical reason why it's not possible for scopes to retain a
pointer to their parent scopes so variables can be looked up that way?
Because the parent scope will be gone by the time closure is called.
Unless we retain a copy of it - which in most cases is very expensive
and impractical - you usually don't need all variables from parent scope

you need 1-2 of them, keeping all of them linked to the closure - and
thus not freed until closure ceases to exist - would be very expensive.
Declaring shared variables explicitly is a trade-off allowing you to not
keep all the variables in case you do not need them.

I am not sure but it is too expensive only for memory. I don't think
that current scope will be very big and operation for copying it very
slowing because we work with memory (correct me if i not right). Often
we don't to know what variables will be needed in future. And seems to
me that can to detect which variables bound in closure and copy only it.
Many people use PHP not because it very fast and because it very simple
to use. Syntax must be more clear for support. And using additional
keyword for a bound with variables it's not doing it.

At now this is there should not alter of course. What really needed is
'named parameters'

For example

function some_action($var1 = 0, $var2 = 0) ...

If need pass only second parameter i need to do following

some_action(0, $b) ...

Instead of

some_action($var2 = $b) ...

13 years ago by Stas Malyshev — view source

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Hi!

I am not sure but it is too expensive only for memory. I don't think
that current scope will be very big and operation for copying it very

That depends on the scope, it can be very big - e.g. global scope. But
more important is not that it is big by itself, but that it retains
variables that are otherwise to be freed and thus increases overall
memory usage.

we don't to know what variables will be needed in future. And seems to
me that can to detect which variables bound in closure and copy only it.

If you know any way to do it, please tell. Please account for $$var, etc.

Many people use PHP not because it very fast and because it very simple
to use. Syntax must be more clear for support. And using additional
keyword for a bound with variables it's not doing it.

I don't think it's very complex syntax - you just specify the variables.
It takes 1 minute to read the manual and you know how to do it forever.
It's not the rocket science to write use($a, $b).

At now this is there should not alter of course. What really needed is
'named parameters'

That's entirely different topic.

--
Stanislav Malyshev, Software Architect
SugarCRM: http://www.sugarcrm.com/
(408)454-6900 ext. 227

13 years ago by Christopher Jones — view source

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At now this is there should not alter of course. What really needed is
'named parameters'

That's entirely different topic.

https://wiki.php.net/rfc/namedparameters

--
Email: christopher.jones@oracle.com
Tel: +1 650 506 8630
Blog: http://blogs.oracle.com/opal/

13 years ago by Yasuo Ohgaki — view source

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2012/4/13 Yasuo Ohgaki yohgaki@ohgaki.net:

I would rather have this.
function FUNC($a, $b, $c) uses ($d, $e, $f) {}
Then it would be consistent with anonymous function.

Oops.
It became consistent, but there would be no use
with PHP. As it cannot pollute global vars.

--
Yasuo Ohgaki
yohgaki@ohgaki.net

13 years ago by Laruence — view source

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Hi,

2012/4/13 Verbitsky Alexander verbitsky_alexandr@mail.by:

Hi:
I have made a RFC to allow user use T_AS in the closure declaration,
like:

function () use($long as $l,&$long as $r) {

}

here is the RFC: https://wiki.php.net/rfc/useas

any ideas? thanks

Closure is a functional literal that can pull with itself all variables
visible in current scope where it was created. For my opinion using keyword
'use' is not necessary and i would have removed it. If you need different
name of variable maybe you need anonymous function.

You might be used to other language's scoping, but
this is the way PHP works.
closure was not the way PHP works. but now, it has be introduced in PHP

Named function cannot do this, but anyway
function FUNC($a, $b, $c) uses ($d, $e, $f) {}
is like
function FUNC($a, $b, $c) { global $d, $e, $f; }

they do are different, previous is a lexical variable. that means it
equal to the value when the closure is created.

the latter is the value when it was called.

thanks

I would rather have this.
function FUNC($a, $b, $c) uses ($d, $e, $f) {}
Then it would be consistent with anonymous function.

There are methods, so we should be careful though.

Regards,

--
Yasuo Ohgaki
yohgaki@ohgaki.net

--

--
Laruence Xinchen Hui
http://www.laruence.com/

13 years ago by Yasuo Ohgaki — view source

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Hi,

2012/4/13 Laruence laruence@php.net:

Hi,

2012/4/13 Verbitsky Alexander verbitsky_alexandr@mail.by:

Hi:
I have made a RFC to allow user use T_AS in the closure declaration,
like:

function () use($long as $l,&$long as $r) {

}

here is the RFC: https://wiki.php.net/rfc/useas

any ideas? thanks

Closure is a functional literal that can pull with itself all variables
visible in current scope where it was created. For my opinion using keyword
'use' is not necessary and i would have removed it. If you need different
name of variable maybe you need anonymous function.

You might be used to other language's scoping, but
this is the way PHP works.
closure was not the way PHP works. but now, it has be introduced in PHP

Named function cannot do this, but anyway
function FUNC($a, $b, $c) uses ($d, $e, $f) {}
is like
function FUNC($a, $b, $c) { global $d, $e, $f; }

they do are different, previous is a lexical variable. that means it
equal to the value when the closure is created.

the latter is the value when it was called.

Thanks for correction.
I should have mentioned that.

It's only similar that these are importing outside vars
into current scope. Importing is the same, but scope
is not.

I wander if there are any good named function usage
that imports current scope vars.

Regards,

--
Yasuo Ohgaki
yohgaki@ohgaki.net