Guido van Rossum wrote:
It's been tried before without much success. I think it may have been a decade ago that Ka-Ping Yee created a pattern matching library that used function calls ... It didn't get much use.
That may largely be due to marketing issues. A potential user would have to know that Ka-Ping's module existed, or be sufficiently dissatisfied with the status quo to go looking for something like it. Probably it has never even occurred to many people familiar with REs from other contexts that there might be another way. Whereas if there were a set of constructor functions available right at hand in the re module, prominently featured in the examples and reference docs, I suspect they would be used quite a lot. I know that *I* would use them all the time, whereas I've never been motivated enough to pull in another module to get this functionality. Perhaps the best way to think of this is not as a complete replacement for traditional RE syntax, but as a set of convenience functions for building up REs out of smaller REs. It's not entirely straightforward to do that correctly, taking into account escaping, operator precedence, etc., so having some functions available for it makes a lot of sense. They would make it much easier to write readable code involving complicated REs. Since we're a community of people who believe that "readability counts", there shouldn't be any argument that this is a desirable goal.
On the third hand, I could see this as an area where a pure library-based approach will always be doomed, and where a proposal to add new syntax would actually make sense.
I don't think new syntax is necessary -- functions are quite adequate for the task. But they need to be available right at your fingertips when you're working with REs. Having to seek out and obtain a third party library is too high a barrier to entry. -- Greg