Homepage: https://www.gnu.org/software/emacs
Author: Damon Anton Permezel
Towers of hanoi in Emacs
Solves the Towers of Hanoi puzzle while-U-wait. The puzzle: Start with N rings, decreasing in sizes from bottom to top, stacked around a post. There are two other posts. Your mission, should you choose to accept it, is to shift the pile, stacked in its original order, to another post. The challenge is to do it in the fewest possible moves. Each move shifts one ring to a different post. But there's a rule; you can only stack a ring on top of a larger one. The simplest nontrivial version of this puzzle is N = 3. Solution time rises as 2**N, and programs to solve it have long been considered classic introductory exercises in the use of recursion. The puzzle is called `Towers of Hanoi' because an early popular presentation wove a fanciful legend around it. According to this myth (uttered long before the Vietnam War), there is a Buddhist monastery at Hanoi which contains a large room with three time-worn posts in it surrounded by 21 golden discs. Monks, acting out the command of an ancient prophecy, have been moving these disks, in accordance with the rules of the puzzle, once every day since the monastery was founded over a thousand years ago. They are said to believe that when the last move of the puzzle is completed, the world will end in a clap of thunder. Fortunately, they are nowhere even close to being done... 1999 addition: The `Towers of Unix' command (hanoi-unix) stems from the never-disproven legend of a Eunuch monastery at Princeton that contains a large air-conditioned room with three time-worn posts in it surrounded by 32 silicon discs. Nimble monks, acting out the command of an ancient prophecy, have been moving these disks, in accordance with the rules of the puzzle, once every second since the monastery was founded almost a billion seconds ago. They are said to believe that when the last move of the puzzle is completed, the world will reboot in a clap of thunder. Actually, because the bottom disc is blocked by the "Do not feed the monks" sign, it is believed the End will come at the time that disc is to be moved...