Quines (Self-Replicating Programs)

http://www.madore.org/~david/computers/quine.html

by lifthrasiir • 5 years ago

66 20 5 years ago

Normille• 5 years ago

Interesting article. I'd never heard of this concept before and thought "That sounds trivial" until I started to read the article. I must admit though, I gave up halfway through when the C code got too esoteric for me to follow. But still feel I've learned something new today.

The article title seems a bit off though. When I read 'Self-Replicating Programs' [sic] it I immediately thought "Worms" but the article actually refers to programmes which can print out their own source code listing. Which seems to me to be a different challenge.

credit_guy• 5 years ago

When I read 'Self-Replicating Programs' [sic] it I immediately thought "Worms"

You are not wrong at all. At its base, any virus is a quine. Well, both computer viruses and biological viruses are quines. Life itself would not be possible without quines.

cuteboy19• 5 years ago

Source code inspection (or cp) is considered cheating for quines, normal viruses don't follow this rule

darkwater• 5 years ago

```

#!/bin/bash

cat $0

```

susam• 5 years ago

Or as was posted to https://news.ycombinator.com/item?id=29874052 by @jcalvinowens a few hours ago, we can also simplify this to just:

  #!/bin/cat

Example:

  $ echo '#!/bin/cat' > foo
  $ chmod +x foo
  $ cat foo
  #!/bin/cat
  $ ./foo 
  #!/bin/cat

charcircuit• 5 years ago

or just an empty string for various languages

capableweb3• 5 years ago

Wouldn't this be considered cheating according to the submission?

The easiest way to do that, of course, is to seek the source file on the disk, open it, and print its contents. That may be done, but it is considered cheating; besides, the program might not know where the source file is, it may have access to only the compiled data, or the programming language may simply forbid that sort of operations.

2wrist• 5 years ago

Cool! I will have a look.

BTW this was raised in a cracking corecursive episode recently https://corecursive.com/quines-polyglot-code/

nathias• 5 years ago

Anyone interested in this should really read Hoffstadter's Gödel, Escher, Bach.

dwheeler• 5 years ago

The most amazing multi-quine I've seen is the quine relay here: https://github.com/mame/quine-relay

It goes through 128 programming languages to regen its starting point.

yalue• 5 years ago

Fun side fact: that's a project from Yusuke Endoh, who also happens to be the most prolific winner of the the obfuscated C contest (ioccc.org).

siraben• 5 years ago

There is an issue on Nixpkgs to package this absolute (but beautiful) monster of a package.[0]

[0] https://github.com/NixOS/nixpkgs/issues/131492

commandlinefan• 5 years ago

This is the first project I've ever seen with an excuse to declare as many dependencies as it does.

yorwba• 5 years ago

An interesting "application" are zip quines, where a compressed archive decompresses to itself. https://research.swtch.com/zip

I recently built a zip quine that was simultaneously a valid PDF to show off, and the most fun part was making the CRC32 check succeed. If the checksum had been based on a cryptographic hash function, it would've been essentially impossible, but fortunately CRC32 can be reversed simply by solving a system of linear equations.

vsnf• 5 years ago

Quines also play a large part in the Reflections on Trusting Trust essay

https://www.cs.cmu.edu/~rdriley/487/papers/Thompson_1984_Ref...

carapace• 5 years ago

Joy lang has a particularly beautiful quine:

    [[dup cons] dup cons]

You run it with the i combinator:

    [[dup cons] dup cons] i
     [dup cons] dup cons
     [dup cons] [dup cons] cons
    [[dup cons]  dup cons]

thenthenthen• 5 years ago

Is a forkbomb also a Quine(s)? I love this famous one from Dyne.org[1]: :(){ :|:& };:

[1] https://jaromil.dyne.org/journal/forkbomb_art.html

Quines (Self-Replicating Programs)

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