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Hmm - you know I actually think it's not correct to look at regex as an interface - even though we use it as one. It's really more accurate to look at it as a

Hmm - you know I actually think it's not correct to look at regex as an interface - even though we use it as one. It's really more accurate to look at it as a grammar (type 3 if I remember correctly). Anything that comes out of the whole chomskian hierarchy stuff isn't going to look intuitive. But the point is that it is a particular, very rigorously defined system of representation. And various systems of representation are always more or less intuitively accessible - and come with a whole set of trade offs around what they can represent vs their ease of use etc... These things just are - written into the laws of the world. They are discovered - not invented. We pick them up and use them as we would rocks left lying around. We find better ones when we can and fashion better ones when we can too...

arnsholt 14y ago
> Anything that comes out of the whole chomskian hierarchy stuff isn't going to look intuitive. Why not? Type-0 (recursively enumerable) languages are equivalent to Turing machines, and we've managed to invent some pretty good syntaxes for that. The main problem with regexes really is the syntax. Regular languages are a lot easier to understand (IMO) if you look at the left/right-linear grammars that define the same language as the regex. Regex syntax as a representation is very close to the FSA used for matching, and that's not necessarily the representation best suited for human consumption.
praptak 14y ago
> These things just are - written into the laws of the world. They are discovered - not invented. This applies only to the theoretical computer science regexes. The practical regexes are very different in this aspect. Practical regexes are neither discovered nor invented - they are constructed. The theoretical regexes are just the basis but on top of that there's a lot of features added. Some of them are just syntactic sugar for theoretical regexes but others actually make the language non-regular. Groups that match what previous named groups have matched are definitely in this category.

arnsholt 14y ago

> Anything that comes out of the whole chomskian hierarchy stuff isn't going to look intuitive. Why not? Type-0 (recursively enumerable) languages are equivalent to Turing machines, and we've managed to invent some pretty good syntaxes for that. The main problem with regexes really is the syntax. Regular languages are a lot easier to understand (IMO) if you look at the left/right-linear grammars that define the same language as the regex. Regex syntax as a representation is very close to the FSA used for matching, and that's not necessarily the representation best suited for human consumption.

praptak 14y ago

> These things just are - written into the laws of the world. They are discovered - not invented. This applies only to the theoretical computer science regexes. The practical regexes are very different in this aspect. Practical regexes are neither discovered nor invented - they are constructed. The theoretical regexes are just the basis but on top of that there's a lot of features added. Some of them are just syntactic sugar for theoretical regexes but others actually make the language non-regular. Groups that match what previous named groups have matched are definitely in this category.