Jon Cantwell
Stuff & Things. Mostly devtricks slides for synacor.
4+1 ThingS
I bet you didn't know were turing-complete
what is turing-completenesss?
- tl;dr: "Turing-complete" means something's at least as powerful as a Turing Machine
- A Turing Machine is a model of computation - given any algorithm, one can construct a TM to compute that algorithm.
- Equivalent to the lambda calculus (Church-Turing Thesis)
- TM : Assembly :: Lamba Calculus : Lisp
- (and ultimately, assembly and Lisp are precisely as powerful as one another)
- Any programming language is going to be Turing-complete (even so-called Turing Tarpits. even SQL!)
- But those are boring...
html5 and css3
- Near & dear to our heart as webdevs
- http://jsfiddle.net/Camilo/eQyBa/
- can implement the Rule 110 Cellular Automaton, which is TC (about which more later)
- despite being a declarative markup language, declarations interact just enough
http://my-codeworks.com/blog/2015/css3-proven-to-be-turing-complete
cellular automata
- Might be familiar from AoC...
- Grid of cells, on/off
- State at step N+1 for a cell is determined by the state of cells in the original cell's neighborhood (usually 'adjacent', sometimes 'orthogonally adjacent', according to some rule
game of life
- One of the most famous cellular automata (and TC), although not the simplest TC cellular automaton
- TC implemented on Game of Life is definitely a party (more, plus details)
- Other class of CAs referred to by integer rules coding for binary instructions about what to do next
rule 110
| curr: | 111 | 110 | 101 | 100 | 011 | 010 | 001 | 000 |
|---|---|---|---|---|---|---|---|---|
| new: | 0 | 1 | 1 | 0 | 1 | 1 | 1 | 0 |
- Winds up generating highly-ordered systems, neither totally ordered nor totally chaotic, that are provably Turing-Complete (proof)
Magic the gathering
- It is actually possible, working entirely within the constraints of card rules, using creatures as the tape, hacking card text w/ Artificial Evolution, to implement a Turing Machine using Magic cards.
- It's pretty ludicrous.
honorable mentions
- Braid is undecidable (TC)
- Infinite Minesweeper is, too
- Minecraft and Dwarf Fortress are, but neither of those is really surprising - not even hard to build a CPU in Minecraft, and Dwarf Fortress, well...
just the x86 'mov' instruction
- It has been alleged that the x86 instruction set is baroque and overcomplicated...
- ...but it's possible to implement a transport-triggered architecture just by taking advantage of promiscuous addressing modes of x86 mov (proof)
and finally...
believe it or not,
PHP
4+1 Things I Bet You Didn't Know Were Turing-Complete
By Jon Cantwell
