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Date: Wed, 15 Nov 2006 20:56:08 +0100
Reply-To: Marcus Boerger <helly@php.net>
Message-ID: <1583529945.20061115205608@marcus-boerger.de>
To: Mathias Bank <phpinternals@thunder-2000.com>
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Subject: Re: [PHP-DEV] Re: Feature-Request - Macros
From: helly@php.net (Marcus Boerger)

Hello Mathias,

  we would need a lexer/parser that support changing rules. That would mean
changing bothtools. Eventhough that might happen if there are other reasons
to do so,the toolswe change todo not necessarily support whatyou woule need.
Based on our current experience re2c and lemon would be a big step forward
as they also allow unicode handling. However i doubt that you can easily
allow changing rules in lemon.

Another solution would be to have your functionality as a stream operation.
That is an extension could rewrite the incoming script while it is being
compiled. I have however no idea if and how that could be achieved.

best regards
marcus

Wednesday, November 15, 2006, 6:06:42 PM, you wrote:

> Mathias Bank schrieb:
>> Hallo,
>> 
>> you know, that there was often a discussion about a "ifsetor" function. 
>> I want to generalize this discussion. If you know LISP, there is a 
>> fantastic macro function which allows you to generate own syntax (not a 
>> c macro function, which is really bad). It would be fantastic, if php 
>> could implement such a macro function. One example (for ifsetor): you 
>> could define
>> 
>> macro ifsetor($param1, $param2) {
>>    return "if (isset($param1)) return $param1; else return $param2;
>> }
>> 
>> use: $test = ifsetor($_GET["blubb"],null);
>> 
>> All you have to do is to not execute the parameters given in the macro 
>> parameter list. Instead, you have to evaluate the return statement and 
>> then to execute this statement.
>> 
>> In this way, all discussions about ifsetor (or anything like this) could 
>> be avoided.
>> 
>> The macro function could even be extended to allow new blocks, but then 
>> we have to extend the syntax to allow reference to the body. In this 
>> way, I always extend the syntax of the parameter data: only variables 
>> would be matched.
>> 
>> macro foreachkey($array as $key, :body $body) {
>>   return "foreach ($array as $key=>$__dev0) {
>>        $body
>>      }";
>> }
>> 
>> know, you can call
>> $secondArray = array();
>> foreachkey($myArray as $myKey) {
>>     $secondArray[] = $myKey;
>> }
>> 
>> this would be extended to
>> foreach ($myArray as $myKey=>$__dev0) {
>>   $secondArray[] = $myKey;
>> }
>> 
>> and this code will be executed.
>> 
>> As you see, with this macro functions, it could be achieved any 
>> individual syntax. It would be a pleasure, if php could support it. It 
>> could shorten a lot of code.
>> 
>> Mathias

> I have recieved a few mails which have shown, that some people 
> misunderstood my idea. It seems, that most of you know c/c++ macros. But 
> I don't want to implement these macro functionality, because this 
> functionality is really poor. Have a look at the macro functionality of 
> lisp: 
> http://www.gigamonkeys.com/book/macros-standard-control-constructs.html 
> and http://www.gigamonkeys.com/book/macros-defining-your-own.html. 
> There, it is described, what macros in lisp can do. You will see, that 
> such macros cannot be compared with c/c++ macros. But it would be a 
> pleasure for php, if such macros would be possible. You should really 
> read it, I couldn't believe it until I have realized it at my own.

> PHP is a really great language and the syntax is much better than the 
> syntax of lisp. But the macros are one big pleasure in lisp. And don't 
> mistake lisp macros for c macros. They are much more powerful.

> Mathias




Best regards,
 Marcus