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Date: Wed, 14 Aug 2013 13:44:15 +0200
Message-ID: <CALtuQzDCunbtDtYbR1Qo+hWHH40prj=B59NJjgehy4x4BjU73Q@mail.gmail.com>
To: Anthony Ferrara <ircmaxell@gmail.com>
Cc: Stas Malyshev <smalyshev@sugarcrm.com>, Julien Pauli <jpauli@php.net>, 
	"internals@lists.php.net" <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=e89a8f3ba7e1e17bb304e3e6e248
Subject: Re: [PHP-DEV] [RFC] Constant Scalar Expressions
From: krebs.seb@gmail.com (Sebastian Krebs)

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Hi,

Just asking: Does this cover only declarations, or every constant
expression, for example

$weeks = $secs / (60 * 60 * 24 * 7);

becomes to the opcode-equivalent of

$weeks = $secs  / (604800);

?


2013/8/14 Anthony Ferrara <ircmaxell@gmail.com>

> Stas,
>
>
> On Wed, Aug 14, 2013 at 5:01 AM, Stas Malyshev <smalyshev@sugarcrm.com
> >wrote:
>
> > Hi!
> >
> > >> https://wiki.php.net/rfc/const_scalar_expressions
> >
> > I like the idea, but absence of constant support makes this thing much
> > less useful, as you can't do things like:
> >
> > public $angle = M_PI/2;
> >
> > I think this is one of the reasons this idea was never implemented -
> > because without constant support you're limited to doing things that are
> > quite obvious and trivial.
> >
>
> Yeah, having constants in those expressions would be great. If only
> constants in PHP were actually constant...
>
> But this win is really cheap (a trivial change to the parser), so I figured
> it was worth proposing separately. If we want to add the opcode stream
> later to do expressions for constant values, we can. This just gives us the
> quick win today of allowing relatively trivial, but important expressions.
>
> The biggest wins I see are in power-of-2 math:
>
> class Foo {
>     const FLAG_1 = 1 << 0;
>     const FLAG_2 = 1 << 1;
>     const FLAG_3 = 1 << 2;
>     const FLAG_4 = 1 << 3;
>     const FLAG_5 = 1 << 4;
>     const FLAG_6 = 1 << 5;
>     const FLAG_7 = 1 << 6;
> }
>
> And in other complex formulas where having the self-declaration adds
> semantic meaning.
>
> Now, as far as if it's worth while making the change without constant
> support, that's for each of us to decide. I think it is, but if you don't,
> that's cool too.
>
> Thanks
>
> Anthony
>



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