C implementation of Tic-Tac-Toe in a single call to printf • Hacker News Board

Re: C implementation of Tic-Tac-Toe in a single call to printf

#81

Post by peter_d_sherman » Mon, Jun 08, 2020, 6:25 AM UTC

Holy Crap Batman!

Never in a million years would I have thought that printf() was Turing-Complete -- and yet, here's the proof that it is...

And then there's this related paper:

https://www.usenix.org/system/files/conference/usenixsecurit...

Page 175: "Printf is Turing-complete"

Re: C implementation of Tic-Tac-Toe in a single call to printf

#82

Post by thr0w__4w4y » Mon, Jun 08, 2020, 5:14 PM UTC

avidphantasm wrote: post #65

I am jealous of people who have time to do things like this.

I hear you on that. But for me, the jealousy dissipates quickly once I realize that even if I had /lots/ of time, I don't think I would come up with this.

Re: C implementation of Tic-Tac-Toe in a single call to printf

#83

Post by identity0 » Mon, Jun 08, 2020, 5:32 PM UTC

yjftsjthsd-h wrote: post #80

identity0 wrote: post #76

Earlier quoted context omitted.

Would you say that an infinite loop has infinite lines of code?

It has infinite instructions, yes. (Well, "unbounded" or "endless", if we're being picky.)

No it doesn’t. It has finite instructions for the loop body, and then one jump instruction for the loop.

Re: C implementation of Tic-Tac-Toe in a single call to printf

#84

Post by 7786655 » Mon, Jun 08, 2020, 6:00 PM UTC

JanisL wrote: post #51

JoshTriplett wrote: post #48

Earlier quoted context omitted.

This only works if you're not dealing with Unicode, where the number of bytes, the number of characters, and the width of those characters can all vary.

This makes me wonder if there's some sort of Unicode equivalent for this?

wcwidth()

Re: C implementation of Tic-Tac-Toe in a single call to printf

#85

Post by JanisL » Fri, Jun 12, 2020, 12:14 AM UTC

7786655 wrote: post #84

JanisL wrote: post #51

Earlier quoted context omitted.

This makes me wonder if there's some sort of Unicode equivalent for this?

wcwidth()

Thanks, I wasn't aware of this. Here's a man page for anyone else that was interested: https://man7.org/linux/man-pages/man3/wcwidth.3.html