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Date: Wed, 20 Apr 2016 23:41:54 +1000
Message-ID: <CAF1yvAQ_W02qD_vcbkEzzFh=DpV0h4XF21nGrsmCJrWywjWJzA@mail.gmail.com>
To: Zeev Suraski <zeev@zend.com>
Cc: PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=001a113f8a5cc77c060530eac176
Subject: Re: [PHP-DEV] Re: Improving PHP's type system
From: me@jesseschalken.com (Jesse Schalken)

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On Wed, Apr 20, 2016 at 10:55 PM, Zeev Suraski <zeev@zend.com> wrote:

>
> On 20 =D7=91=D7=90=D7=A4=D7=A8=D7=B3 2016, at 14:54, Jesse Schalken <me@j=
esseschalken.com> wrote:
>
> If I had "scalar", "number" and ?T as types, the types I would need would
> be:
>
>    1. ?scalar|Decimal
>
>
> What's decimal?  I'm not aware we have that type.  Apologies if I missed
> it that it was added.
>

As I said:

I have a function that converts values to SQL which have SQL equivalents,
> including decimal values represented by a special Decimal class. It accep=
ts
> int|string|bool|null|float|Decimal.


All of int|string|bool|null|float can be converted to SQL
straightforwardly, however, MySQL has a distinct decimal type for exact
decimal values, written like "8542.31" in SQL (to get write a float, you
need "8542.31e0"). My class Decimal is used to represent a MySQL value of
type decimal, so it can be passed without be lossily converted to/from
float, and so it can be converted to the correct SQL. It is neither a float
nor an integer. A distinct class is needed for it.

>
>    1. ?scalar|Decimal|Expr
>
>
> What's Expr?  Again I'm not aware that we have that type.
>

As I said:

I have a class Expr which represents an expression in SQL. Expressions can
> be composed of other expressions, and of literal values, so the
> constructors for Exprs accept int|string|bool|null|float|Decimal|Expr.



In both, a nullable scalar does the job.
>
>
>    1. ?scalar|array
>
> Conduct this check in user code, you'd have to anyway.
>

Not if I'm giving it straight to json_encode() I don't.


>
>    1. int|string (I *want* int|string here. I know array keys are always
>    int|string. A wider type is lies.)
>
> This is needlessly purist.  For handling a meaningless con, we'd
> overcomplicate the language and provide a footgun(tm) for everyone.  Not =
a
> good bargain.
>

int|string is the correct type. If you're going to dismiss correctness as
"needlessly purist" then I'm going to dismiss PHP as not intended for
writing correct software.

>
>    1. ?scalar (probably)
>
> Ok
>
>
>    1. number
>
> Ok
>
>
>    1. T|false
>
> You didn't answer my question on this one.
>

substr() returns string|false
file_get_contents() returns string|false
fopen() returns resource|false
strpos() returns int|false
etc..

Without unions, the types of these functions cannot be denoted.


>    1. ?T
>
> Ok
>
> 5 out of 8 still need a union.
>
>
> Actually, in my count only one of them does (#7) and it's probably
> solvable (if it's even a thing), and in another, it makes no sense to use
> types at all (#3) as you'd have to do these checks in userland anyway.  A=
ll
> others can be satisfied just fine with scalar, numeric and nullable types=
,
> unless you're being needlessly purist - and we're not going to
> overcomplicate the language for the sake of purism.
>
> Zeev
>

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