[TUHS] Regular Expressions
will.senn at gmail.com
Sat Aug 1 12:33:39 AEST 2020
Yes, I googled it per Clem's suggestion and wound up on that exact link
after wandering around admiring the scenery. I envy the more
mathematically inclined among us their view of matters technical. This
piece, being in C and having step by step articulation of the diagrams,
is better for me than the more formal wikipedia article, although, when
I get enough background, that looks like it'll be good, too.
Thanks Rob, Clem and Bakul.
On 7/31/20 7:36 PM, Rob Pike wrote:
> I think this link - https://swtch.com/~rsc/regexp/regexp1.html i- s
> the best place to start. Superb exposition on the background, theory,
> and implementation as well as a bit of history of how the industry
> lost its way with regular expressions.
> Regular expressions are beautiful, simple, and widely misunderstood.
> On Sat, Aug 1, 2020 at 10:03 AM Bakul Shah <bakul at iitbombay.org
> <mailto:bakul at iitbombay.org>> wrote:
> On Jul 31, 2020, at 3:57 PM, Will Senn <will.senn at gmail.com
> <mailto:will.senn at gmail.com>> wrote:
> > I've always been intrigued with regexes. When I was first
> exposed to them, I was mystified and lost in the greediness of
> matches. Now, I use them regularly, but still have trouble using
> them. I think it is because I don't really understand how they work.
> > ...
> > 1. What's the provenance of regex in unix (when did it appear,
> in what form, etc)?
> > 2. What are the 'best' implementations throughout unix (keep it
> pre 1980s)?
> > 3. What are some of the milestones along the way (major changes,
> forks, disagreements)?
> > 4. Where, in the source, or in a paper, would you point someone
> to wanting to better understand the mechanics of regex?
> Start here: https://en.wikipedia.org/wiki/Thompson%27s_construction
> [I learned about regular expressions in an automata theory class,
> before I knew anything about Unix. What helped me was learning
> about finite state machines. You won't need more than paper and
> pencil to construct one. Reading source code would make more
> sense once you grasp how to construct a FSM corresponding to a RE.]
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