Rage against the Turing Machine (confoo)

Lightning talk.

Transcript

1. Rage against the Turing Machine
2. Programming is hard
8. 0 0 1 1
9. 0 0 1 1
10. 0 0 1 0
11. 0 0 0 0
12. 0 1 0 0
13. 0 1 0 0
14. 0 1 0 0
15. 0 1 0 0
16. 0 1 0 0
17. 0 1 0 0
18. while (!in_array($state, $accept_states)) { $read_val = isset($tape[$position]) ? $tape[$position] : '_'; ! if (!isset($rules[$state][$read_val])) { throw new NoTransitionException(); } ! list($write_val, $move_dir, $new_state) = $rules[$state][$read_val]; ! $tape[$position] = $write_val; ! if ('l' === $move_dir) { $position--; if ($position < 0) { $position++; array_unshift($tape, '_'); } } else if ('r' === $move_dir) { $position++; if ($position >= count($tape)) { array_push($tape, '_'); } } ! $state = $new_state; }
22. This machine can run any algorithm
23. This machine can run any algorithm etsy.com/shop/sharpwriter
24. Universality
25. add increment one-third
26. add increment one-third add increment one-third
27. add increment one-third
28. add increment one-third U
29. U M
31. Entscheidungsproblem
32. Halts?
33. Halts? Negate
34. Halts? Negate Copy
35. Halts? Negate Copy { X
36. ( ) X X
37. Halts? Negate Copy X
38. Halts? Negate Copy X X
39. Halts? Negate Copy true X X
40. Halts? Negate Copy X ∞ true X
41. Halts? Negate Copy X ∞ true X X X }
42. Halts? Negate Copy false X X
43. Halts? Negate Copy false halting now X X
44. Halts? Negate Copy false halting now X X X X }
45. • Proof by contradiction • Decision machine cannot exist • We are screwed
46. How to cope
48. • Restricted subsets of computing • Finite state machines • Type systems
49. Conclusion
50. Programming is hard