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Date: Thu, 12 Feb 2015 14:31:10 +0000
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To: =?utf-8?Q?Pavel_Kou=C5=99il?= <pajousek@gmail.com>
Subject: Re: [PHP-DEV] [VOTE] Scalar Type Hints
From: ajf@ajf.me (Andrea Faulds)

Hi Pavel,

> On 12 Feb 2015, at 13:48, Pavel Kou=C5=99il <pajousek@gmail.com> =
wrote:
>=20
> C# does have dynamic typing.

No it doesn=E2=80=99t, it=E2=80=99s a statically-typed language. I =
don=E2=80=99t understand why you say it has dynamic typing - there is =
some limited dynamism in parts, but I don=E2=80=99t think it affects =
what we=E2=80=99re talking about. Dynamic typing and polymorphism =
aren=E2=80=99t the same.

> I just don't believe that method overloading would suddenly make
> everyone write poor programs.

Maybe not, but all the facilities needed to make good programs are =
already there. Overloading would only really be useful for writing bad =
programs, because all the good things it enables are already supported =
by PHP.

> It brings cleaner declarations of methods and functions.

Only slightly. A switch() (or better, a pattern match, were we to add =
that) can do the same job and it=E2=80=99s not that much less clean.

> Also, it
> brings the possibility of having operator overloading in user classes
> someday in the future (yes, this can be abused as well, but it also
> has legitimate use cases - like class for representing Money and being
> able to do +, - , / or * operations on them).

Overloading isn=E2=80=99t necessary for operator overloading.

> Is the option of omiting
> type hints and having optional parameters really a good enough
> replacement for method overloading polymorphism for you? Because for
> me, it unfortunately is not. :(

Could you give an example use-case?

> Read the example once more, please - the issue I see with it is that
> bar() requires float, but foo() just number and doesn't convert it to
> the required type. The most unpredictable thing is that it will work
> half of the time and half of the time it will just throw errors.

Well, yes. PHP is dynamically-typed, this can happen, whether you=E2=80=99=
re using strict or weak typing. Your only way to guard against it here =
is to do proper testing. Well, if we added a numeric type hint, your IDE =
could catch this error for you, actually.

Anyway, the same thing can happen for float->int conversions *with* weak =
typing, as we disallow certain conversions (PHP_INT_MIN > $x,  =
PHP_INT_MAX < $x, !isfinite($x), isnan($x)).

Also, even though PHP does allow most float->int conversions with weak =
typing, it doesn=E2=80=99t mean they=E2=80=99re a good idea. Silently =
losing the fractional part is probably not what you want.

Thanks.
--
Andrea Faulds
http://ajf.me/