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Date: Tue, 23 Jul 2019 13:08:59 +0200
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To: Arnold Daniels <arnold.adaniels.nl@gmail.com>
Cc: PHP Internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC] Strict operators directive
From: nikita.ppv@gmail.com (Nikita Popov)

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On Wed, Jul 10, 2019 at 11:38 PM Arnold Daniels <
arnold.adaniels.nl@gmail.com> wrote:

> Hi Nikita,
>
> Thanks for your feedback.
>
> I'll fix the textual errors you mentioned.
>
> * "To compare two numeric strings as numbers, they need to be cast to
> > floats." This may loose precision for integers. It is better to cast to
> > numbers (int or float) using, with the canonical way being +$x. But I
> guess
> > that won't work under strict_operators. Maybe we should have a (number)
> > cast (it already exists internally...)
> >
>
> Good point. While in most cases you know if you're working with floats or
> integers, adding a way to cast to either an int or float would be nice.
> Maybe preferably through a function like `numberval($x)` or simply
> `number($x), so the `(type)` syntax is reserved for actual types. That
> would be an RFC on its own though.
>
>
> > * This has already been mentioned by others: Having $str1 < $str2 perform
> > a strcmp() style comparison under strict_operators is surprising. I think
> > that overall the use of lexicographical string comparisons is quite rare
> > and should be performed using an explicit strcmp() call. More likely than
> > not, writing $str1 < $str2 is a bug and should generate a TypeError. Of
> > course, equality comparisons like $str1 == $str2 should still work,
> similar
> > to the distinction you make for arrays.
> >
>
> Ok, fair. I'll change it so <,<=,>,>=,<=> comparison on a string throws a
> TypeError, similar to arrays, resources, and objects.
>
>
> > * If I understand correctly, under this RFC "foo" == 0 will throw a
> > TypeError, but ["foo"] == [0] will return false. Generally the behavior
> of
> > the recursive comparison here is that it's the same as strict == but all
> > errors become not-equal instead. Correct? I'm not sure how I feel about
> > this, as it seems to introduce one more set of semantics next to the weak
> > ==, strict == and === semantics there already are.
> >
>
> The syntax would be `$a == $b` (or `$a == [0]`), where $a and $b are a
> string/int in one case and both an array in the other case. In the second
> case, we can't throw a TypeError as both operands are of the same type.
>

You can, if you treat == comparisons recursively, which is how I personally
would expect them to work. There shouldn't be a difference in behavior
between $a == $b and [$a] == [$b] -- either both should throw TypeError if
$a and $b have different types, or neither should.

> * I also find it somewhat odd that you can't write something like "$obj !=
> > null" anymore, only "$obj !== null".
> >
>
> To check against null, it's better to use !==. For objects (and resources)
> using `!= null` is ok, but for other types, it's currently not. For
> example; `[] == null` gives true.
>
>
> > * I think the "solution" to the last three points is a) only support
> > numbers in relational operators (<,<=,>,>=,<=>) and throw TypeErrors
> > otherwise (maybe modulo provisions for object overloading) and b) allow
> > comparing any types in == and !=, without throwing a TypeError. The
> > question "Are 42 and 'foobar' equal?" has a pretty clear answer: "No they
> > aren't", so there is no need to make this a TypeError (while the question
> > "Is 42 larger than 'foobar'?" has no good answer.) I believe doing
> > something like this would roughly match how Python 3 works. (Edit: I see
> > now that this is mentioned in the FAQ, but I think it would be good to
> > reconsider this. It would solve most of my problems with this proposal.)
> >
>
> Besides the argument in the FAQ, having the == and != return do a type
> check, means there are a lot more cases where the behavior changes rather
> than that a TypeError is thrown. Currently `"foobar" == 0` returns true,
> but this would make it return false. So would `1 == true`, `"0" == 0` and
> `"0" == false`. To reduce the cases where the behavior changes to a
> minimum, it's better to throw TypeErrors for == and !=.
>

Yes, I can certainly see how that would be an issue. I think both variants
have pretty major issues and there may not be a good solution here. In that
case I we might want to consider banning == and != entirely under
strict_operators mode and force the use of === and !== which will have the
usual well-defined semantics.

I think that would cause the least overall confusion and wouldn't even be a
particularly large loss in terms of functionality. I think the only really
useful behavior of == (that is not available with ===) under this proposal
was the non-identity object comparison.

Nikita

> * String increment seems like a pretty niche use case, and I believe that
> > many people find the overflow behavior quite surprising. I think it may
> be
> > better to forbid string increment under strict_operators.
> >
>
> Ok
>
>
> > * A similar argument can be made for the use of &, | and ^ on strings.
> > While I have some personal fondness for these, in practical terms these
> are
> > rarely used and may be indicative of a bug. I think both for string
> > increment and string and/or/xor it may be better to expose these as
> > functions so their use is more explicit.
> >
>
> These operators make it very easy to work with binary data as strings in
> PHP. In other languages you have to work with byte arrays, which is a major
> pain. They're also very intuitive; `"wow" & "xul"` is the same as
> `chr(ord('w') & ord('x')) . chr(ord('o') & ord('u')). chr(ord('w') &
> ord('l'))`. I think these should stay.
>
>
> >
> > Regards,
> > Nikita
> >
>
> Arnold
>

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