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Date: Thu, 13 Feb 2014 15:56:11 +0800
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To: Christian Stoller <stoller@leonex.de>
Cc: Davey Shafik <davey@php.net>, "internals@lists.php.net" <internals@lists.php.net>, 
	Simon J Welsh <simon@simon.geek.nz>
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Subject: Re: [PHP-DEV] [RFC] Combined Comparison Operator
From: tjerk.meesters@gmail.com (Tjerk Meesters)

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On Thu, Feb 13, 2014 at 3:19 PM, Christian Stoller <stoller@leonex.de>wrote:

> Davey Shafik <davey@php.net> wrote:
> > This adds a new operator "(expr) <=> (expr)" that returns 0 if both
> > operands are equal, 1 if the left is greater, and -1 if the right is
> > greater.
> >
> > It works with all types (just as well as <, <=, >=, > work) and is great
> > for usort() callbacks for example.
> >
>
> Why not using `$a - $b` instead of `$a <=> $b`?
>

This only works on numbers, and integers in particular, because of how the
result of a comparison function is cast.

For example, `0.4f - 0.5f` equals `-0.1f` but gets cast to `0` when it's
converted to a long value.

See also: http://lxr.php.net/xref/PHP_5_6/ext/standard/array.c#597


>
> Simon J Welsh <simon@simon.geek.nz> wrote:
> > The only real case I see for this is to save some boilerplate when
> > dealing with arrays. Strings have strcmp(), numbers have subtraction
> > And when you're sorting objects, you probably want to be doing
> > the comparison on some string/numeric property.
> >
>
> Agreed! It would make more sense to write a comparison function for
> arrays/objects.
>
>
> Best regards
> Christian
>



-- 
--
Tjerk

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