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Date: Thu, 19 Dec 2013 22:42:43 +0000
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Subject: Re: [PHP-DEV] Re: power operator (again)
From: rowan.collins@gmail.com (Rowan Collins)

On 19/12/2013 22:16, Daniel Macedo wrote:
>> No, the average PHP developer is going to do $var ** 2 and it will
>> >behave exactly as they expect with negative values. Yes, in the very
> I didn't quite understand if you're making the case for assuming a type
> casting of $var and keep with the expected math or if operator precedence
> would mean the result could be negative in some cases.

I understood Rasmus's point to be rather simpler than that: PHP code 
will rarely contain the actual hard-coded sum "-3 ** 2", it will much 
more likely look something like this:

$var = some_function();
$square_of_var = $var ** 2;

Now if some_function() returns -3 (the integer), $square_of_var will end 
up with a value of 9. No need to worry about associativity, no type 
casting, just application of maths, and the result is as expected.

Now, you could imagine a more complex example like this:

$cube_of_inverted_var = -$var ** 3;

But that's hard enough to read that I'd probably introduce brackets 
anyway, if not avoid the unary operator altogether:

$cube_of_inverted_var = (-1 * $var) ** 3;

In my head, the reason "-3 ** 2" looks like (-3) ** 2 is that I tend to 
think of "-3" as a single literal value, not the application of the 
unary operator "-" to the literal value "3". Once it becomes "-$var ** 
2", that impression evaporates, and I would, personally, avoid assuming 
precedence one way or another, and add some brackets.

Regards,

-- 
Rowan Collins
[IMSoP]