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RE: Type hints with null default values

php.internals

Cristiano Duarte

21 years ago

Marcus Boerger wrote:

> Hello Robert,
>
> Tuesday, October 19, 2004, 10:20:59 PM, you wrote:
>
>> The issues surrounding this seemed to have been muddied up a little, I'll
>> try to clear them up.
>
>> I see two different sets of functionality that people are asking for.
>
>> #1. The ability to pass null on a type hinted param (but still a
>> #mandatory
>> param)
>
>> #2. The ability to define an optional type hinted param.
>
>> I see it as a very important distinction to make. Using the #2 to solve
>> #1 is not the solution PHP should implement. Using some method which
>> operates on the class hint itself is the right solution.
>
>> For example, using the [] method:
>
>> public function Compare([BaseClass] $objA, $cmpFunc);
>
> As far as we disallow this and only allow optional types at the end i'd
> agre to this. Example:
>
> public function Compare($cmpFunc, [BaseClass] $objA);
>

I don't see any danger if we allow null with this syntax:

 public function Compare([BaseClass] $objA, $cmpFunc);

if we don't allow null with this syntax:

 public function Compare(BaseClass $objA, $cmpFunc);

and if we make an argument optional with this syntax:

 public function Compare($cmpFunc, BaseClass $objA=null);

If someone (like me) has thousands lines of code that uses 'null' meaning
'null reference' just need to use syntax #1.

If someone is very strict and don't even think about using null in
typehinted arguments, because null is not a value it's a type and must be
used as so, just need to use syntax #2.

If someone wants to make typehinted parameters optional, just use syntax #3.

I really don't see any problem allowing this three syntaxes(but I'm not very
clever since I'm for syntax #1) :-P

Regards,

Cristiano Duarte

Cristiano Duarte

21 years ago

So reading all posts on this subject, the proposal would be:

1) Allow null typehints
public function Compare([BaseClass] $objA, $cmpFunc);

Ex: Compare(null, 'func1');

2) Don't allow null typehints
public function Compare(BaseClass $objA, $cmpFunc);

Ex: Compare(new BaseClass(), 'func1');

3) Optional argument (with typehint)
public function Compare($cmpFunc, BaseClass $objA=null);

Ex: Compare('func1');

Am I right ?  Is it possible to implement all three syntaxes ?
IMH it would satisfy everybody's needs.

Regards,

Cristiano Duarte

Marcus Börger

21 years ago

Hello Cristiano,

Wednesday, October 27, 2004, 2:21:03 AM, you wrote:

> So reading all posts on this subject, the proposal would be:

> 1) Allow null typehints
>  public function Compare([BaseClass] $objA, $cmpFunc);

see below.

> 2) Don't allow null typehints
>  public function Compare(BaseClass $objA, $cmpFunc);

>  Ex: Compare(new BaseClass(), 'func1');

> 3) Optional argument (with typehint)
>  public function Compare($cmpFunc, BaseClass $objA=null);

This is no option because BaseClass typehint doesn't allow null and if
we have a dedicated syntax for default values we don't need this.

If at all this would be:
4) public function Compare($cmpFunc, [BaseClass] $objA=null);

But first we need to know if we really want to allow passing null
with default typehinted values. Since there is no concept of null
references in PHP. Having a value of null to mark not passed is
a nice differentiation.

So for now the only addition we may probably consider for 5.1 is
adding 4: optional typehinted values that default to null and only
null.

marcus

Christian Schneider

21 years ago

Marcus Boerger wrote:

> So for now the only addition we may probably consider for 5.1 is
> adding 4: optional typehinted values that default to null and only
> null.

Please don't add another parameter syntax (especially with line-noi...
err special characters) like [BaseClass]. This would make PHP more
unreadable than it needs to be for a minor feature. To allow
foo(BaseClass $objA = null) to also accept foo(null); handles the few
cases where you want to pass null nicely IMHO.

Advocating to only change the PHP syntax to simplify it,
- Chris

Curt Zirzow

21 years ago

* Thus wrote Christian Schneider:

> Please don't add another parameter syntax (especially with line-noi...
> err special characters) like [BaseClass]. This would make PHP more
> unreadable than it needs to be for a minor feature. To allow
> foo(BaseClass $objA = null) to also accept foo(null); handles the few
> cases where you want to pass null nicely IMHO.

I'd have to agree, that changing the syntax on how to pass optional
class type hints, is probably not a good thing to do.  It has been
traditional to set a parameter to default by assigning a value to
the paramater, and the rule always has been what kind of value can
be assigned.


Curt

--
Quoth the Raven, "Nevermore."

Sebastian Bergmann

21 years ago

Marcus Boerger wrote:

> So for now the only addition we may probably consider for 5.1 is
> adding 4: optional typehinted values that default to null and only
> null.

That sounds like the most sane way to do it.

--
Sebastian Bergmann                      http://www.sebastian-bergmann.de/
GnuPG Key: 0xB85B5D69 / 27A7 2B14 09E4 98CD 6277 0E5B 6867 C514 B85B 5D69

Andi Gutmans

21 years ago

At 10:53 AM 10/27/2004 +0200, Christian Schneider wrote:

>Marcus Boerger wrote:
>>So for now the only addition we may probably consider for 5.1 is
>>adding 4: optional typehinted values that default to null and only
>>null.
>
>Please don't add another parameter syntax (especially with line-noi... err
>special characters) like [BaseClass]. This would make PHP more unreadable
>than it needs to be for a minor feature. To allow foo(BaseClass $objA =
>null) to also accept foo(null); handles the few cases where you want to
>pass null nicely IMHO.
>
>Advocating to only change the PHP syntax to simplify it,

Yeah I tend to agree. Adding [] for a not that popular case seems not to be
worth it. It just adds more complexity to the syntax.
I suggest to either leave as is or to support default values of NULL (only)
and if that is given then you may also pass NULL (give it a double meaning).

Andi

Cristiano Duarte

21 years ago

Andi Gutmans wrote:

> At 10:53 AM 10/27/2004 +0200, Christian Schneider wrote:
>>Advocating to only change the PHP syntax to simplify it,
>
> Yeah I tend to agree. Adding [] for a not that popular case seems not to
> be worth it. It just adds more complexity to the syntax.
> I suggest to either leave as is or to support default values of NULL
> (only) and if that is given then you may also pass NULL (give it a double
> meaning).

Will be possible to implement this "null default value" with "double
meaning" for 5.1? Just as information, since it would help me a lot.

Cristiano Duarte

Unnamed Person

21 years ago

What was the result of this discussion?

Thanks

On 27 Oct 2004, at 12:50, Andi Gutmans wrote:

Marcus Börger

21 years ago

Hello Cristiano,

Friday, October 22, 2004, 7:41:24 PM, you wrote:

> If someone (like me) has thousands lines of code that uses 'null' meaning
> 'null reference' just need to use syntax #1.

Then you are simply using your PHP tool wrong. PHP is not Java where you
need (and have) null references.

Best regards,
Marcus                            mailto:helly@php.net