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Instead of learning $bullet_point_count regular expressions by rote, just learn how they work and make your own as you need them. They really aren't hard to use

Instead of learning $bullet_point_count regular expressions by rote, just learn how they work and make your own as you need them. They really aren't hard to use, they're just incredibly compact, which makes them look unintelligible at first. _Mastering Regular Expressions_ is the obvious classic, but a decent intro to Perl or Python will probably get to them eventually. (If you use Emacs, it's particularly easy to learn them by experimenting with M-x re-builder.) Also: Not everything uses the same RE implementation, some use non-standard extensions. Don't become too drunk with power yet, though! There's a lot they're just not capable of doing (most notably, balancing tags around arbitrarily nested expressions). Once you have REs down, learning a lexer/parser is the next step. :)

tdavis 18y ago
Exactly! Learn how to write regular expressions because they are super useful, then immediately disregard the boiler-plate ones provided in this article because any self-respecting language's stdlib (or extremely common libraries/frameworks) will handle all these specific cases in an abstracted way. Not to mention, learning only these doesn't mean you understand regex and not all the features of most regex engines are covered here (lookaheads, lookbacks, etc. and so on)
gruseom 18y ago
If you use Emacs, it's particularly easy to learn them by experimenting with M-x re-builder. Hey! I did not know about this, and it looks really useful. I've used http://www.newartisans.com/blog_files/regex.tool.for.emacs.php http://www.newartisans.com/blog_files/regex.tool.for.emacs.p... and it's good, but not as well integrated. I wish I knew a better way to get a survey of what's available in the Emacs world - something that would have clued me in to this command, for example... any tips? Edit: I want to comment on this as well: learning a lexer/parser is the next step Recently I've had occasion to write a few parsers. In the past, I'd always used parser generators (yacc and antlr) on the assumption that they made things easier. For this project that wasn't an option, so I bit the bullet and did the recursive descent thing. To my surprise, it turned out to be way, way easier than I expected. Moreover, in at least one case (a complex one), the hand-written parser code turned out shorter than the (cl-) yacc version, as well as handling more cases and reporting errors better. The morals of the story are: (1) Don't assume something is hard without trying it; (2) It's not hard to write a classical recursive-descent parser and the skill is a lot more useful than you may realize. Wish I'd learned that a long time ago.
- litewulf 18y ago
  That being said, RDPs have quite a bit of boilerplate that may obscure your grammar. (And small bugs in a RDP are sometimes very hard to catch...)
- mark_h 18y ago
  I wish I knew a better way to get a survey of what's available in the Emacs world - something that would have clued me in to this command, for example... any tips? http://planet.emacsen.org/ http://planet.emacsen.org/ often has useful stuff. The emacs wiki (http://emacswiki.org/ http://emacswiki.org/) is often where you end up after googling and has a heap of information (although even it isn't complete!). You could try http://www.emacswiki.org/cgi-bin/wiki/RandomPage http://www.emacswiki.org/cgi-bin/wiki/RandomPage when you're bored :)
- silentbicycle 18y ago
  I second Emacswiki as suggested, but I find quite a bit by searching through the Emacs and Elisp info pages and using M-x apropos / M-x apropos-variable. It doesn't always work though - to find something, you generally need to know what Emacs calls it.
Darmani 18y ago
If I understand what you mean, you actually can balance tags around arbitrarily nested expressions if your regex parser supports recursion. The Ruby Way has an example of using recursive regexes to balance parentheses.
- silentbicycle 18y ago
  Once your regexes are getting that complicated, though, you're probably better off specifying things in terms of a BNF-based parser (or a recursive-descent parser, depending on the grammar).
jimbokun 18y ago
The article seems like a good tutorial for learning regex constructions, with the examples chosen good motivation for learning.

tdavis 18y ago

Exactly! Learn how to write regular expressions because they are super useful, then immediately disregard the boiler-plate ones provided in this article because any self-respecting language's stdlib (or extremely common libraries/frameworks) will handle all these specific cases in an abstracted way. Not to mention, learning only these doesn't mean you understand regex and not all the features of most regex engines are covered here (lookaheads, lookbacks, etc. and so on)

gruseom 18y ago

If you use Emacs, it's particularly easy to learn them by experimenting with M-x re-builder. Hey! I did not know about this, and it looks really useful. I've used http://www.newartisans.com/blog_files/regex.tool.for.emacs.php http://www.newartisans.com/blog_files/regex.tool.for.emacs.p... and it's good, but not as well integrated. I wish I knew a better way to get a survey of what's available in the Emacs world - something that would have clued me in to this command, for example... any tips? Edit: I want to comment on this as well: learning a lexer/parser is the next step Recently I've had occasion to write a few parsers. In the past, I'd always used parser generators (yacc and antlr) on the assumption that they made things easier. For this project that wasn't an option, so I bit the bullet and did the recursive descent thing. To my surprise, it turned out to be way, way easier than I expected. Moreover, in at least one case (a complex one), the hand-written parser code turned out shorter than the (cl-) yacc version, as well as handling more cases and reporting errors better. The morals of the story are: (1) Don't assume something is hard without trying it; (2) It's not hard to write a classical recursive-descent parser and the skill is a lot more useful than you may realize. Wish I'd learned that a long time ago.

litewulf 18y ago
That being said, RDPs have quite a bit of boilerplate that may obscure your grammar. (And small bugs in a RDP are sometimes very hard to catch...)
mark_h 18y ago
I wish I knew a better way to get a survey of what's available in the Emacs world - something that would have clued me in to this command, for example... any tips? http://planet.emacsen.org/ http://planet.emacsen.org/ often has useful stuff. The emacs wiki (http://emacswiki.org/ http://emacswiki.org/) is often where you end up after googling and has a heap of information (although even it isn't complete!). You could try http://www.emacswiki.org/cgi-bin/wiki/RandomPage http://www.emacswiki.org/cgi-bin/wiki/RandomPage when you're bored :)
silentbicycle 18y ago
I second Emacswiki as suggested, but I find quite a bit by searching through the Emacs and Elisp info pages and using M-x apropos / M-x apropos-variable. It doesn't always work though - to find something, you generally need to know what Emacs calls it.

Darmani 18y ago

If I understand what you mean, you actually can balance tags around arbitrarily nested expressions if your regex parser supports recursion. The Ruby Way has an example of using recursive regexes to balance parentheses.

silentbicycle 18y ago
Once your regexes are getting that complicated, though, you're probably better off specifying things in terms of a BNF-based parser (or a recursive-descent parser, depending on the grammar).

jimbokun 18y ago

The article seems like a good tutorial for learning regex constructions, with the examples chosen good motivation for learning.