Re^3: Perl 6 grammar question

However in Perl 5 we are introducing [given] through a module(.pm) file which is pretty much different than controlling the parser itself.

That's wrong on two levels.

First, all the module does is to flip a switch that controls whether the parser treats given as a keyword or not. feature most definitely controls the parser itself.

Secondly, it makes no sense to say that adding keywords dynamically is a good thing and to say that adding keywords using a module is a bad thing. It's a contradiction.

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Re^4: Perl 6 grammar question by Anonymous Monk on Mar 12, 2010 at 08:43 UTC
U'r right, but I never implied adding them through a module is bad or adding them dynamically is good. Of course such features, although powerful must be used with caution and judiciously. That is true for any powerful but use-with-caution feature. What I meant was, take for example 'given', it can be implemented in a module using if/else statements. Here what you are doing is using existing features of a language to build more abstract features. This is good as well... But my point was that this is not the same as controlling the parsing itself. I would not like start a debate on which of them is better. Users are best to decide on that. To put it more appropriately if there is more than a way to achieve it, its better.	[reply]
Re^5: Perl 6 grammar question by ikegami (Patriarch) on Mar 12, 2010 at 09:03 UTC
This is good as well... But my point was that this is not the same as controlling the parsing itself. I know, and it's not always true. In theory, the module could control the parser to create said if/then structure, and that would be great. It's even possible to do this in Perl5 using source filters. When you using filters, you need to provide a parser. Seeing as you have to write the parser, you are definitely controlling it. What I meant was, take for example 'given', it can be implemented in a module using if/else statements Unfortunately, not really. Perl5 is not expendable in that manner without using source filters. Filters replace the builtin parser. That means you need to completely reimplement a Perl parser if you want that resembles Perl. That's what Switch does and that's why it's a source of headaches. What you actually want is integration into the existing parser, starting with the ability to add keywords. And that's what Perl6 can do. * — Perl doesn't differentiate modules from scripts. It's all Perl code.	[reply]
Re^5: Perl 6 grammar question by Corion (Patriarch) on Mar 12, 2010 at 08:47 UTC
Actually no - the syntax of `given` can not be implemented in Perl through a module¹. You can use source filters to rewrite the program, like Switch did, but you will then get all the problems that are associated with source filters. ¹ Discounting Devel::Declare, which for Perl 5.10 tries to allow new keywords through modules. Update: Arunbear tells me that Devel::Declare only requires Perl 5.8.1, so modifying the parse process might be possible even there.	[reply] [d/l]
Re^6: Perl 6 grammar question by Anonymous Monk on Mar 12, 2010 at 09:00 UTC
I think your original comment The main thing is that you can introduce new keywords, something which is not easy to do otherwise. Was a correct way to say it	[reply]