Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:113088
To: Benjamin Morel <benjamin.morel@gmail.com>,
 "G. P. B." <george.banyard@gmail.com>
Cc: PHP internals <internals@lists.php.net>
References: <CAFPFaMKDELHFr44kOncQWeCi7KZUL7XLNL2JyvJvmNLTgjDBOQ@mail.gmail.com>
 <CAG9XoMTc-7axJBQu2Skt6ng+6pU4o7gsXy+J47C5EeXyZLmZ=A@mail.gmail.com>
Message-ID: <86b1f50b-2ac0-bc92-96b3-d79480262539@allenjb.me.uk>
Date: Fri, 5 Feb 2021 10:58:46 +0000
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101
 Thunderbird/78.7.0
MIME-Version: 1.0
In-Reply-To: <CAG9XoMTc-7axJBQu2Skt6ng+6pU4o7gsXy+J47C5EeXyZLmZ=A@mail.gmail.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Content-Language: en-GB
Subject: Re: [PHP-DEV] [RFC] Warning for implicit float to int conversions
From: php.lists@allenjb.me.uk (AllenJB)

On 04/02/2021 17:54, Benjamin Morel wrote:
> On Thu, 4 Feb 2021 at 17:05, G. P. B. <george.banyard@gmail.com> wrote:
>
>> Greetings internal,
>>
>> I'm proposing a new RFC which would warn when an implicit conversion
>> from float to int occurs.
>>
>> The draft is currently located on GitHub:
>> https://github.com/Girgias/float-int-warning/
>> for ease of commenting/providing changes to it.
>>
>> The official discussion phase wouldn't start before I convert it to 
>> docwiki
>> and
>> post it on the wiki, something I'm planning to do next week.
>>
>> Any feedback is appreciated.
>>
>> Best regards,
>>
>> George P. Banyard
>>
> Hi George,
>
> Thank you for this proposal, I'm all for it, though I'd go one step
> further, and actually issue a warning during explicit casting as well:
>
> (int) 3.5; // E_WARNING
> (int) round(3.5); // OK
>
> In my experience, it's better to be explicit about your intent, so forcing
> the user to round() before casting when the float has a fractional part is
> OK to me.
> This would help prevent weird silent conversions such as when you cast to
> (int) from user input:
>
> $age = $_GET['age']; // '25.75'
> $x = (int) $foo; // I'd expect a warning, not a silent conversion to 25
>
> — Benjamin


There are legitimate cases for explicitly casting floats to int. For 
example floor() outputs a float, but in the context of the domain I'm 
working I might know that the result is never going to exceed a certain 
value and want the result explicitly as an int.

(And after checking the manual, I'd also note here that round() also 
returns a float, so how exactly does your example here work? Is it only 
OK to explictly cast a float that's the return value of a function? Or 
only explictly cast a float if the fractional part is .0? Is that viable 
given the "inaccuracy" of floats? Or would it be better for PHP to have 
some non-range/accuracy-sensitive representation for integers (and 
decimals) here?) (and now we're getting into "why are we still using 
floating point math by default in 2021" territory, so I'll stop right here)

AllenJB


PS. Apologies for the dupe to those who did receive my original send, 
but I forgot to amend my from address to my subscribed address and as I 
recall the list doesn't like list-only replies)