Chess written in sed | Hacker News Reader

Chess written in sed

github.com

112 pointstphd51 comments

At one time, I became interested in the Turing-completeness of sed, and I started working on primitives for flow control and function calls. Then, I came to my senses.

There's an error in line 1024. The transform strings are not the same length.

I'd like to see more sed programs on HN instead of the usual Python, Ruby or Go offerings.

I wrote a sed version of the the Python script "youtube-dl". This way I don't need Python installed to download YouTube videos. And it's easy to edit if YouTube suddenly changes their "API"; no need to wait for someone else to fix their Python or Lua script. In truth, it's not pure sed though. It uses sh (not bash), sed and ftp (or any other http client that handles 302's).

Are you frequently on a unix platform without python? Just out of interest.

I agree its nice to see a variety of languages. Gives a fresh perspective on how to do things.

Yes.

I never need to install Python permanently.[1] In my experience, there is almost always a way to do what needs to be done with what UNIX provides, without installing more software. This keeps the system smaller, more standardized and hence more portable than one where various dependencies are haphazardly added.

1. Sometimes I have to install it temporarily, for "reverse engineering" a non-Python solution, e.g., when someone decides to use Python as a substitute for make.

Ya totally! I still telnet to my servers... Don't want to fill my system with extra software. :P

Not sure I understand your comment.

Like sed, all UNIX systems provide ssh. It's not "extra software". There's no need to use telnet.

On the other hand, not all UNIX systems have Python pre-installed. Moreover, as in the case of embedded products, not all systems may have the space for it.

Neither do I

You have to use Unicode sed.

Ah. Thanks. I just assumed a strictly POSIX sed would work. My mistake.

either it's fixed or you are having unicode issues. looks fine to me.

This is a bit like that fellow who did pixel art by manually writing coloured table cells in HTML in Notepad - very, very impressive, but it does make one wonder a little about the person who has done it.

>very, very impressive, but it does make one wonder a little about the person who has done it.

it has deep roots in the psyche of my old country:

http://en.wikipedia.org/wiki/The_Tale_of_Cross-eyed_Lefty_fr...

Many thanks for posting this - it's enlightening context. :)

Do you have a link to that?

I saw the video many years ago, and a search just now seems to only find links to a video that has disappeared from YouTube.

There's an English translation (in .doc) at the bottom of the wikipedia article:

http://www.auburn.edu/~mitrege/russian-culture/lefty.doc

There appears to be a bug. Here is the state I reached (notice that "white" now has two bishops of the same color).

      a b c d e f g h
    8 ♖ ♘ ♗ ♕ ♔   ♘ ♖ 
    7 ♙ ♙ ♙ ♙ ♙ ♗     
    6                 
    5             ♙   
    4     ♝ ♟ ♟       
    3               ♙ 
    2 ♟ ♟ ♟     ♟ ♟ ♟ 
    1 ♜ ♞ ♝   ♚   ♞ ♜

Someone want to submit a pull request? :-)

edit: For anyone who wants to reproduce ("black" went first, since black appears as white on the board)

    1. e4 h5
    2. d4 h4
    3. Bb4 h3
    4. Qf3 g5
    5. Qxf7 Bxf7??

I just tried this in real life and got the same bug. Hmmm.

It also seems to allow some illegal moves. The computer moved its bishop like a rook.

On my first game I got an even better bug:

  a b c d e f g h

8 ♔ ♛ ♝ ♘

7 ♙ ♙ ♙ ♙

5 ♙

4 ♟ ♟ ♕

3 ♟ ♞

2 ♟ ♟ ♟ ♟

1 ♜ ♛ ♚ ♝ ♜

After performing en passant the computer went crazy and the King started taking all the pieces between down row 8. I ended up with a very easy checkmate as I walked my pawn the remaining three rows, unfettered even when it was under double pressure from the night and queen.

I wonder if this is perhaps an issue caused by the fact I used OS X's BSD sed.

Edit: Hmm, can't seem to format it right. Anyways, the bug seems to be present in gnu sed as well. Really the whole game was screwy. I started with e2 e4 and it all went down hill from their for my opponent :).

The readme says passant isn't implemented, and there's no validation of the player's moves. So you did an illegal move.

Interesting. Either way my opening seemed to be more problematic as the computer still went out of its way to checkmate itself without the en passant. Still a cool achievement.

Also see: http://uuner.doslash.org/forfun/sedtris.sed

sed, and also awk, and ed, are worth learning. I mean coding a chess game in those tools is just a novelty, but you can do so much really useful text processing with just those tools, and they are pretty much guaranteed to be available on almost any *nix machine.

What's an example of something non-interactive that ed is good for that you can't easily do with other tools?

OK I'll bite. For this answer I'll assume "easily" to mean "with less typing".

ed has a more concise syntax for joining arbitrary lines of a file (by line number or pattern) and then saving the file (by way of a temp file in $TMPDIR). You could do this with awk and perhaps with other standard tools (note: I don't consider perl to be "standard"). But I think it's safe to say the ed script would always be shorter. ed's syntax for deleting and moving arbitrary lines is similarly concise. For these specific tasks, it's not going to be easy to win at code golf using awk or other tools... and in some cases it may be impossible.

Hey cool, thanks. I've always overlooked it.

I use sed in makefiles, to scrape the source code for a version number, and then embed that version number in the name of the executable to be built. That would be easy enough in, say, Python, but as a sed script it's lightweight, decently readable, and puts everything you need to know right there in the makefile.

That said, I've recommended learning Python to a few people, but have never even suggested anybody learn sed or awk.

Oh, yeah, sed and awk are great, I meant ed in particular.

That's true... but I haven't had to do real work on a system that didn't already have Python installed on it in a long time.

novelty yes, but let's not detract from the man's prowess; writing a chess game in sed is entirely non-trivial.

Would be interested for someone to fork this and translate the cyrillic to english

Was going to comment the same thing. This seems like it could be really neat, but with all of the comments in a language I can't read, I'm not entirely sure what to think, haha.

I Google translated the README.md, but fixed a few translatorisms.

https://github.com/zeckalpha/SedChess

Of course it was done by somebody Russian.

Actually, Russians are quite pragmatic, as most other xUSSR people. So this is a rare counter-example, I believe.

Guess that beats Tic-Tac-Toe in awk

http://awk.info/?doc/tictactoe.html

For bonus points, guess what this sed script does:

http://pastie.org/8261668

(hint: see line 14.)

Just a wild guess: would it be the asteroids game?

Nope, try again. ;p

It looks like it doesn't implement the input-accepting comma operator!

I love how he felt compelled to excuse his omission of castling and en passant moves by explaining that they were added to chess "later" (14th and 15th century)... maybe he started working on this project before those rules were added? :)

I don't want to detract from how absolutely awesome this is, but there are definitely some bugs in this.

- It routinely moves bishops vertically.

- It lets you make illegal moves yourself (not a huge deal).

- I got a square turning black for no reason.

Might also be nice if it told you what move it just made.

First thing that come to my mind when I read the title.

Programmer who did something like that is mad. Or he/she is from Russia.

I love that anything new was done with sed.

Hurrah for novelty usage of unix command line tools.

It's, like, really really bad at chess.

"The marvel is not that the bear dances well, but that the bear dances at all."

and if you make illegal moves, it just moves again

This is more about being very good at sed than bad at chess, really :)

This is almost more exciting than church numerals

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