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Date: Sun, 02 May 2004 18:39:21 +0200
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Subject: Re: [PHP-DEV] [RFC] Type hints
From: thekid@thekid.de (Timm Friebe)

On Sat, 2004-05-01 at 22:09, Marcus Boerger wrote:
> Hello internals,
> 
>   while working with php 5 the last days i find it more and more
> annoying that we allow NULL with type hints.
> From my perspective allowing NULL with typehints would happen 
> only very rare.

I don't think this is true. I think there are a number of cases where
passing NULL is used to "unset" or "delete" something. For example, say
a class supports debugging using a listener model:

  class Foo {
    function setEventListener(Listener $l) { ... }
  }

  $foo= new Foo();
  $foo->setEventListener(new ConsoleListener());
  // ...
  $foo->setEventListener(NULL);

This makes perfect sense to me and also gets rid of the constraint of
having to define an "unsetEventListener" method.

To wrap it up: Would you agree that being able to pass NULL to any
pointer argument in C is annoying?

[...]
> 2) (Andi) introduce 'not null' after php 5.0. This won't introduce
> a BC break. But it would require two new keywords 'NOT' and 'NULL'.
> The latter is not a problem because it is a define at the moment
> and the patch (a) shows that it easy to change it into a keyword.
> The problem is the new keyword 'not' which would introduce a BC
> break for everyone using the word 'not' already.

I like this idea best: No magic such as "only when it is the first
default argument" (the question "why" will inevitably come up sooner or
later); plus no BC break.

Concerning the new keyword argument, how about using the exclamation
mark (already meaning "not"), as in:

* function foo(Classname !NULL $val) { }
  The same as Andi's suggestion, but using ! instead of "not"

* function foo(Classname $val !NULL) { }
  Ditto, but using postfix notation. Comes close to default value
  syntax which people are already used to.

* function foo(Classname $val != NULL) { }
  This would be even more similar to the default value syntax.

- Timm