Lisp implementation in sed

[mseri]

Ahahah. Awesome. There is even an 'awk' version: https://github.com/darius/awklisp

[abecedarius]

I wrote that, and I gotta say sed is a much crazier target.

More sed fun: http://aurelio.net/projects/sedsokoban/

[mtdewcmu]

That's kind of funny, because awk is already a programming language.

[nate_martin]

Would someone mind giving a quick explanation of how this works? I have only used sed to replace text in files and directories. How do people write interpreters and game loops with this unix utility?

[mtdewcmu]

With difficulty.

I started playing with the idea of making a programming language out of sed at one point, but then I decided that, even if I succeeded, it would be a waste of time.

I didn't take into account Hacker News.

[rmorell]

sed is provably Turing complete: http://www.catonmat.net/blog/proof-that-sed-is-turing-comple... which means that it's effectively able to simulate any other Turing-complete language (provided enough processing power and memory).

[jes5199]

the sed language allows conditional jumps to labels. That makes it powerful enough to write programs in.

If you had to just write programs by running a series of sed substitution expressions to a file over and over, and not use conditionals... it might still be possible to program in. Much harder to think about, though.

[asgard1024]

Wouldn't the opposite - stream editor (programmable) in Lisp - be more useful?

[aaronem]

Well, if you count Emacs in batch mode, such a thing already exists.

[justinator]

Well, OK: I'm curious, can I use the sed to Perl utility, to then make a Lisp implementation in Perl?

[justinator]

Trying this myself, it returns an error:

    s2p: expression #1: extra characters after command (d)

Thankfully, I've never had the job of porting a sed script to Perl, so I'm not exactly sure what that's all about. The docs mention this error, but don't explain what it means,

http://perldoc.perl.org/s2p.html

[justinator]

Aaaaand, obviously Perl has CPAN, so there's really no need (except to be evil):

https://metacpan.org/pod/CljPerl

(there's a few, actually, because TIMTOWTDI!)

[bndr]

This is amazing. Just reading the code makes my head hurt, but you implemented a language with it.

[lengads]

Here, for example, is the implementation of `atom` (I think):

  /(atom /{
    /\[\S\+\]/{
      s/.*/[]/
      bpop_context
    }
    s/.*/t/
    bpop_context
  }

[bane]

So I guess if all languages are eventually converging on Lisp, are all Lisps eventually converging on sed? Is sed the bottom turtle or are there more?

[IvyMike]

Now you have three problems.

[krapp]

Oh come on. They took an unreadable language and implemented a slightly less unreadable language in it. That's at least two problems and one solution.

To what, I don't know.