Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:81664
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
Received-SPF: pass (pb1.pair.com: domain gmx.de designates 212.227.17.20 as permitted sender)
Message-ID: <54CFFC5D.4000802@gmx.de>
Date: Mon, 02 Feb 2015 23:38:21 +0100
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0
MIME-Version: 1.0
To: Thomas Bley <mails@thomasbley.de>, dmitry@zend.com
CC: ajf@ajf.me, nikita.ppv@gmail.com, internals@lists.php.net
References: <20150202210349.6FB91261948@dd15934.kasserver.com><54CFE965.2080905@gmx.de> <20150202214254.BEB88261948@dd15934.kasserver.com>
In-Reply-To: <20150202214254.BEB88261948@dd15934.kasserver.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Subject: Re: [PHP-DEV] What do we need strict scalar type hints for?
From: cmbecker69@gmx.de (Christoph Becker)

Thomas Bley wrote:

> Yes, we currently have negative values for invoices and positive for vouchers ...
> 
> 
> Christoph Becker wrote on 02.02.2015 22:17:
> 
>> Thomas Bley wrote:
>>
>>> Here is a typical billing example which uses exceptions:
>>>
>>> <?php
>>> ini_set('error_reporting', E_ALL);
>>> ini_set('display_errors', 1);
>>>
>>> addVat('apples');
>>>
>>> function addVat($amount) {
>>>   if (!is_int($amount) && !is_float($amount)) {
>>>     throw new InvalidArgumentException('Argument 1 passed to '.__FUNCTION__.'
>>>     must be of the type int|float, '.gettype($amount).' given');
>>>   }
>>>   return round($amount*1.19, 2);
>>> }
>>>
>>> Instead of multiple strict scalar hints (e.g. function addVat(int|float
>>> $amount){...}), I would prefer to have "numeric" as strict type:
>>> function addVat(numeric $amount){...}
>>
>> Have you considered
>>
>>  addVat(-1);

Well, my point was that even a strict type system doesn't necessarilly
catch all erroneous/undesired arguments.  Even if addVat() properly
handles negative numbers, and maybe even zeroes, there are functions
that can't.

IMHO strict typing in a dynamic language is overvalued.  While it
certainly helps to catch some errors, it doesn't do so during compile
time, at least not for all cases (consider call_user_func() etc.)[1]

And frankly, I don't see what's wrong with a weak type hint in this case:

  function addVat(float $amount) {...}

You're returning a float, anyway.

[1] There may be other benefits of having strict type hints.  One of
these would be potential optimizations, but I have some doubts whether
this is feasible with optional weak/strict type hinting on the *call* side.

OTOH, strict type hints would require a lot of manual conversions.

-- 
Christoph M. Becker