[awirth]

This reduction is really cool. I love reductions like this.

Is there a general consensus to use "regular expression" to refer to the actual regular ones and "regex" to refer to the non-regular variants?

[zokier]

I think Raku (neé Perl 6) has been spearheading that distinction

https://docs.raku.org/language/regexes (see the intro paragraph)

[robinhouston]

This distinction was introduced by Jeffrey Friedl’s book _Mastering Regular Expressions_ (2006), and it seems to be fairly commonly used now.

[awirth]

Too late to edit, but out of curiosity I re-implemented this to use the PCRE JIT (in PHP) to see what kind of speedup it would provide: https://gist.github.com/allanlw/69df509519335b88db886d48503a...

Timings for fred.cnf on my machine:

python: 0m53.744s

PHP (no PCRE JIT): (hits backtrack limit in 1m15.994s)

PHP (PCRE JIT): 0m20.109s

[chubot]

I wouldn't say so, but I use the term "regular language" if I mean the mathematical concept.

[robinhouston]

I don’t think it’s pedantic to say that a regular language is not the same thing as a regular expression. The difference between syntax and semantics is real and important.

[chubot]

(late reply) Right that's what I'm saying. Who said it was pedantic? :)

[gnulinux]

But a "regular language" is not the same as "regular expression" as mathematical concepts.

[chubot]

(late reply) Hm you've negelected to do the obvious thing and explain the difference.

I don't think there's a difference, and if there is one, it's probably not relevant to programming. Whereas the one I'm highlighting is relevant to programming.

[praptak]

I don't think so. Usually you can tell from the context:

# math and/or computer science texts? It's the regular ones.

# pretty much elsewhere? It's the extended ones.

# threads about parsing HTML with regular expressions? People using both and insisting their version is the only correct one.

[gbacon]

Yes, for at least ten years and likely much longer.

https://cstheory.stackexchange.com/q/448/362

[awirth]

Interesting, I wasn't aware of the history.

Personally I make the distinction, but I've noticed many many people do not, hence the question.

[gbacon]

People without theoretical CS background probably think of regular expressions (or regexes for short) as just text-matching thingies that sometimes give you two problems and would look at you blankly if you mention the Chomsky hierarchy. When we don’t know there’s a distinction to be made, we go for economy of expression.

[stevefan1999]

Isn't it PCRE that we started to call it regex?