←2005-04-27 2005-04-28 2005-04-29→ ↑2005 ↑all
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17:18:44 <Keymaker> yo
17:21:17 <Keymaker> why does nothing cool happen?
17:32:01 <fizzie> I've been idly writing a befunge compiler thing, but it still generates buggy code and has issues with self-modification. Trying to fix it enough that it'd run my utm.bef.
17:32:18 <Keymaker> hmm
17:32:18 <lindi-> hmm
17:32:31 <Keymaker> what makes it hard to write a befunge compiler?
17:32:39 <Keymaker> (writing a compiler would be way too hard for me!)
17:32:51 <Keymaker> but is there something different with befunge?
17:33:52 <fizzie> There's the amount of self-modification in the language, so you basically have to include a compiler with the compiled program to recompile affected parts on the 'put' instruction.
17:34:14 <Keymaker> hmm
17:34:16 <lindi-> indeed
17:34:58 <fizzie> This is written in Java, I was going to target Java-bytecode so I could include the same compiler classes with the "executable". Currently I just have (for testing) a _really_ simple C-generating backend, which doesn't handle self-modification at all.
17:36:22 <fizzie> And, as said, creates buggey code. Probably one of my optimization passes. I do some stack-content-analysis to avoid writing conditional jumps that never get taken, and to do constant-folding.
17:37:34 <Keymaker> hmmmm.. sounds confuseing
17:39:03 <lindi-> fizzie: hmm, can you please try to develop it with gcc so that there's a better chance that the final version will also work with gcc? ;)
17:40:07 <fizzie> Ergh. It uses Java-1.5 generics, you know.
17:41:51 <lindi-> fizzie: rright, and that's not even merged to gcc cvs HEAD yet...
17:45:25 <fizzie> Hmmmmn. My befunge source is buggy, too.
17:48:05 <fizzie> fis@colin:~$ ./out
17:48:05 <fizzie> abA!6!0!a!1!A!R!0!b!5!b!R!1!a!1!a!R!1!b!2!b!R!2!a!2!a!R!2!A!3!A!L!2!!!3!!!L!3!a!4!A!L!4!a!4!a!L!4!b!4!b!L!4!A!0!A!R!5!A!7!A!L!5!!!7!!!L!6!aabaa!
17:48:08 <fizzie> accept.
17:48:11 <fizzie> fis@colin:~$ ./out
17:48:13 <fizzie> abA!6!0!a!1!A!R!0!b!5!b!R!1!a!1!a!R!1!b!2!b!R!2!a!2!a!R!2!A!3!A!L!2!!!3!!!L!3!a!4!A!L!4!a!4!a!L!4!b!4!b!L!4!A!0!A!R!5!A!7!A!L!5!!!7!!!L!6!aabaaa!
17:48:16 <fizzie> reject.
17:48:19 <fizzie> Yay. :)
17:48:32 <Keymaker> ??
17:49:27 <fizzie> See http://gehennom.org/~fis/utm.html for the program I was running, and http://gehennom.org/~fis/out.c.txt for the generated code. :p
17:50:19 <Keymaker> ah, this -- although i have no idea how it works
17:50:25 <Keymaker> :)
17:50:54 <Keymaker> must go to eat, will be back soon, at least for a while
18:59:45 <puzzlet> Is that Universal Turing Machine?
19:00:48 <puzzlet> And, what a viewer
19:09:01 <Keymaker> well, couldn't come back earlier
19:09:26 <Keymaker> could someone point me a link that would describe what is universal turing machine and how does it work?
19:12:07 <fizzie> Well, in befunge-93 it has a maximum tape length of ~52, maximum alphabet size of 17 and maximum state limit of 8, so it's not much of an universal turing machine. With an unlimited playfield it would be, though.
19:14:01 <Keymaker> link..?
19:14:45 <fizzie> Well, wikipedia's http://en.wikipedia.org/wiki/Turing_machine page has a description.
19:15:23 <fizzie> Actually I'm not sure that could be called an universal turing machine, since it's not a turing machine, it's a befunge program. It can still simulate any given Turing machine, though.
19:18:37 <Keymaker> thanks
19:18:44 <Keymaker> i try to understand some bits
19:18:45 <Keymaker> :)
19:52:42 <Keymaker> too confusing..
19:52:56 <Keymaker> probably should read something Turing Machines for Dummies
19:52:59 <Keymaker> or something
20:05:40 <Keymaker> rggh.
20:29:45 <fizzie> Take an 'introduction to computer science' course. :) (I probably wouldn't have chosen a universal turing machine as a befunge test-program if I weren't going to t-79.148 now.)
20:30:19 <Keymaker> well, can't do that for a year..
20:30:22 <Keymaker> or something
20:30:36 <Keymaker> i'm not at university yet, too bad
20:31:06 <Keymaker> but thanks for the tip
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←2005-04-27 2005-04-28 2005-04-29→ ↑2005 ↑all