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problem with double as array index?

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  problem with double as array index? "M. Strobel" <strobel@example.com> - 2015-05-06 22:25 +0200
    Re: problem with double as array index? "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-05-06 22:57 +0200
    Re: problem with double as array index? adam <adam@nospam.net> - 2015-05-06 21:12 +0000
      Re: problem with double as array index? "M. Strobel" <strobel@example.com> - 2015-05-07 00:45 +0200
        Re: problem with double as array index? "Christoph M. Becker" <cmbecker69@arcor.de> - 2015-05-07 01:08 +0200
          Re: problem with double as array index? "M. Strobel" <strobel@example.com> - 2015-05-07 13:36 +0200

#15293 — problem with double as array index?

I stumbled upon this problem when trying to define a trivalent logic:

Interactive test:

php > if (! define('triFalse',0))    trigger_error('Error defining!');
php > if (! define('triMaybe',0.5))  trigger_error('Error defining!');
php > if (! define('triTrue', 1))    trigger_error('Error defining!');
php >
php > $triNotarray = array(triFalse=>triTrue, triMaybe=>triMaybe, triTrue=>triFalse);
php > var_dump($triNotarray);
array(2) {
   [0] =>
   double(0.5)
   [1] =>
   int(0)
}

Where is my Maybe value?
I was not aware of this problem (not coding PHP for some time), what is it?

Here the php -v output:

PHP 5.4.20 (cli)
Copyright (c) 1997-2013 The PHP Group
Zend Engine v2.4.0, Copyright (c) 1998-2013 Zend Technologies
     with Xdebug v2.2.6, Copyright (c) 2002-2014, by Derick Rethans

/Str.

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#15294

M. Strobel wrote:

> I stumbled upon this problem when trying to define a trivalent logic:
> 
> Interactive test:
> 
> php > if (! define('triFalse',0))    trigger_error('Error defining!');
> php > if (! define('triMaybe',0.5))  trigger_error('Error defining!');
> php > if (! define('triTrue', 1))    trigger_error('Error defining!');
> php >
> php > $triNotarray = array(triFalse=>triTrue, triMaybe=>triMaybe,
> triTrue=>triFalse);
> php > var_dump($triNotarray);
> array(2) {
>   [0] =>
>   double(0.5)
>   [1] =>
>   int(0)
> }
> 
> Where is my Maybe value?

You're triMaybe is there; triFalse is missing, however.

> I was not aware of this problem (not coding PHP for some time), what is it?

Firstly, a simplification:

  var_dump(array(0 => 'foo', 0.5 =>'foo', 1 => 'foo'));

Explanation: when a float is used as array key, it is cast to int, see
<http://php.net/manual/en/language.types.array.php#language.types.array.syntax>.
 So the second element overwrites the first element.

-- 
Christoph M. Becker

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#15295

On 2015-05-06, M. Strobel <strobel@example.com> wrote:
> I was not aware of this problem (not coding PHP for some time), what is it?
It is not a bug, it is a feature. :)

Array key in PHP can either be an integer or a string. So when you use 0.5 it 
gets auto-casted to an int which gives 0, so:

array (0=>1, 0.5=>2, 1=>3) would be equivalent to array (0=>1, 0=>2, 1=>3)

No magic here.

http://php.net/manual/en/language.types.array.php

Regards,
A.

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#15296

On 06.05.2015 23:12, adam wrote:
> On 2015-05-06, M. Strobel <strobel@example.com> wrote:
>> I was not aware of this problem (not coding PHP for some time), what is it?
> It is not a bug, it is a feature. :)
>
> Array key in PHP can either be an integer or a string. So when you use 0.5 it
> gets auto-casted to an int which gives 0, so:
>
> array (0=>1, 0.5=>2, 1=>3) would be equivalent to array (0=>1, 0=>2, 1=>3)
>
> No magic here.
>
> http://php.net/manual/en/language.types.array.php
>
> Regards,
> A.
>
Okay, got it, index can be an integer or a string, with automatic cast.

You have to be an extremely good programmer to circumvent traps like this, so kudos 
to all PHP programmers writing stable and correct programs.

/Str.

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#15297

M. Strobel wrote:

> On 06.05.2015 23:12, adam wrote:
>
>> Array key in PHP can either be an integer or a string. So when you use
>> 0.5 it
>> gets auto-casted to an int which gives 0, so:
>>
>> array (0=>1, 0.5=>2, 1=>3) would be equivalent to array (0=>1, 0=>2,
>> 1=>3)
>>
>> No magic here.
>>
>> http://php.net/manual/en/language.types.array.php
>
> Okay, got it, index can be an integer or a string, with automatic cast.
> 
> You have to be an extremely good programmer to circumvent traps like
> this, so kudos to all PHP programmers writing stable and correct programs.

Do I read some irony or even sarcasm here?

Anyhow, even for average PHP programmers like me, there are helpful
tools such as PHPUnit[1].  A simple unit test could check the expectations.

[1] <https://phpunit.de/>

-- 
Christoph M. Becker

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#15298

On 07.05.2015 01:08, Christoph M. Becker wrote:
> M. Strobel wrote:
>
>> On 06.05.2015 23:12, adam wrote:
>>
>>> Array key in PHP can either be an integer or a string. So when you use
>>> 0.5 it
>>> gets auto-casted to an int which gives 0, so:
>>>
>>> array (0=>1, 0.5=>2, 1=>3) would be equivalent to array (0=>1, 0=>2,
>>> 1=>3)
>>>
>>> No magic here.
>>>
>>> http://php.net/manual/en/language.types.array.php
>>
>> Okay, got it, index can be an integer or a string, with automatic cast.
>>
>> You have to be an extremely good programmer to circumvent traps like
>> this, so kudos to all PHP programmers writing stable and correct programs.
>
> Do I read some irony or even sarcasm here?

I am just trying to cheer up the PHP people. Stupid PHP bashing is below me.

>
> Anyhow, even for average PHP programmers like me, there are helpful
> tools such as PHPUnit[1].  A simple unit test could check the expectations.

You should start with defensive coding, by which I mean parameter checking, 
returncode checking. You can see in my first post that success of define is checked.

Then, of course, the tests.

/Str.

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