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Date: Thu, 06 Sep 2012 09:52:39 +0200
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Subject: Re: [PHP-DEV] Moving to an AST-based parsing/compilation process
From: ivan.enderlin@hoa-project.net ("Ivan Enderlin @ Hoa")

Hi Dmitry,

On 06/09/12 07:37, Dmitry Stogov wrote:
> Hi Nikita,
>
> Personally, I don't see any reason to build AST. As you mentioned=20
> yourself, it will be slower and will require more memory. On the other =

> hand AST itself would allow to perform only very basic optimizations.=20
> Most of them can be easily done on VM opcode level as well.
The lexing and parsing processes will not be slower than actual, and the =

construction of an AST is a new process. Well, as usual, new process=20
requires new resources. But if we look further, it will certainly be a=20
nice tool to perform better opcode caching, it will remove a lot of=20
hacks, it will allow third-part tools working on safeness, security,=20
quality etc. to go deeper at low-costs which is very important for PHP=20
community, it will facilitate future works (implementations, features=20
etc.) for PHP=85 Moreover, it may be possible that compiler compilers hav=
e=20
a better lexing and parsing processes than actual?

Someone said that AST is more =93academical=94, yes it is and that is why=
 we=20
can benefit from already done researches in this area to avoid memory=20
overhead (one among others). We are not the first ones facing this=20
problem. It requires some researches before starting to develop this.=20
Let's try as a POC and we will quickly see if this is a wrong way or not.=


Cheers.


>
> Also, as it's not an easy task, the old "ugly hacks" will be replaced=20
> with new mistakes, which would require new "hacks" in the future :)
>
> The only real advantage could be an ability to expose AST to PHP=20
> scripts, but only few people may need it.
>
> Thanks. Dmitry.
>
> On 09/04/2012 11:57 PM, Nikita Popov wrote:
>> Hey folks!
>>
>> Some people asked me what the advantages of using an AST-based
>> parsing/compilation process are, so I put together a few quick notes
>> in an RFC:
>>
>> https://wiki.php.net/rfc/ast_based_parsing_compilation_process
>>
>> It would be nice to get a few comments from other core devs on this.
>>
>> Nikita
>>
>
>

--=20
Ivan Enderlin
Developer of Hoa
http://hoa.42/ or http://hoa-project.net/

PhD. student at DISC/Femto-ST (Vesontio) and INRIA (Cassis)
http://disc.univ-fcomte.fr/ and http://www.inria.fr/

Member of HTML and WebApps Working Group of W3C
http://w3.org/