quines—programming your way back to where you were

Programming your wayback to where you were

Riviera.rb5 March 2013

Jean-Baptiste Mazon@jbmazon

Introduction

● What● Cheats● Hacks● Language features

A quine is a computer program which takes no input and produces a copy of its own source code as its only output.

The standard terms for these programs in the computability theory and computer science literature are self-replicating programs, self-reproducing programs, and self-copying programs.

Well-known pattern

D

R

Y

Well-known pattern

Do

Repeat

Yourself

IOCCC 1994: smr

IOCCC 1994: smr

(categorized: Worst Abuse of the Rules)

The recursive aproach

(live demo)

ASCII quine

(live demo)

Generic quine

(but it's still ASCII-based)

(live demo)

A brief math digression

● Fixed-point theorem● Cool functions to fix

– print source

– interpret

– compile

– gzip source

Quines

Quines

Quines

Quine

Quine

● “Yields falsehood when preceded by its quotation” yields falsehood when preceded by its quotation.

Quine

● “Yields falsehood when preceded by its quotation” yields falsehood when preceded by its quotation.

● quine “hello”.→ hello “hello”.

Terminology

● code● data● intron

Bootstrapping

Multiquines

Examples

Examples

● (λx.xx) (λx.xx)

Examples

● (λx.xx) (λx.xx)● #!/bin/sh

cat $0

Examples

● (λx.xx) (λx.xx)● #!/bin/sh

cat $0● #!/bin/cat

Examples

● (λx.xx) (λx.xx)● #!/bin/sh

cat $0● #!/bin/cat● puts(s = <<e, s, 'e')

puts(s = <<e, s, 'e')e

Examples

● (λx.xx) (λx.xx)● #!/bin/sh

cat $0● #!/bin/cat● puts(s = <<e, s, 'e')

puts(s = <<e, s, 'e')e

● Q

Other examples

Final thoughts

● incompleteness● trusting trust● Quine Central● backup● introspection● anything else?

References

● Wikipedia● David Madore's quine page● C2● Russ Cox's “Zip Files All The Way Down”● Dan Piponi's “Quine Central”