1 Aug
2020
1 Aug
'20
9:07 a.m.
Oh, and one good google over another, I also found this:
https://www.drdobbs.com/architecture-and-design/regular-expressions/1844109…
Which is also great and simple to follow :).
Will
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.
-rob
On Sat, Aug 1, 2020 at 10:03 AM Bakul Shah <bakul(a)iitbombay.org
<mailto:bakul@iitbombay.org>> wrote:
On Jul 31, 2020, at 3:57 PM, Will Senn <will.senn(a)gmail.com
<mailto:will.senn@gmail.com>> wrote:
--
GPG Fingerprint: 68F4 B3BD 1730 555A 4462 7D45 3EAA 5B6D A982 BAAF
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.]