3 ms·

How does this work?

• kwantam 16y ago
  It's a deterministic finite automaton (state machine) for dividing by seven. In effect, it's the graph expansion of a regular expression. http://blog.vkistudios.com/index.cfm/2008/12/30/Regular-Expression-to-determine-if-a-base-10-number-is-divisible-by-3 http://blog.vkistudios.com/index.cfm/2008/12/30/Regular-Expr...
  • eru 16y ago
    By the way, at http://slexy.org/view/s2QFWeNxZo http://slexy.org/view/s2QFWeNxZo is a (horrible) regular expression you can pop into "grep -xe" to test decimal numbers for divisibility by 7. (Found with a Haskell programm I wrote via conversion from the DFA.)