[TxMt] Regexp assistance

[Allan Odgaard]

On 26/5/2006, at 11:19, Geir-Tore Lindsve wrote:

> [...] I'm trying to figure out a way to parse a string with an  
> expression, so that I can filter out subexpressions to build up a  
> structure of expression objects.

If I understand correctly, this is not a task for regular expressions.

Regular expressions are for parsing “flat” syntax, i.e. w/o recursive  
constructs. As soon as recursion enters the picture, you need a real  
parser [1].

Such parser is fairly simple to write, but I personally have grown  
rather attached to ANTLR for generating parsers. In TextMate  
snippets, scope selectors, my plist derivative (in the bundle  
editor), and format strings (for regexp replacements) are all parsed  
using an ANTLR generated parser -- I did write some of them by hand  
initially, but if there is the slightest chance the grammar needs to  
be extended in the future, it’s not worth it -- also, when first you  
have learned to use a parser tool, creating a new parser is fairly  
trivial.


[1] http://en.wikipedia.org/wiki/Recursive_descent_parser