Thursday, 11 December 2008

Equality, containment and intersection among regular expressions via symbolic manipulation

Three standard regular expression operations

data RE a where
Phi :: RE a -- empty language
Empty :: RE a -- empty word
L :: a -> RE a -- single letter taken from alphabet a
Choice :: RE a -> RE a -> RE a -- r1 + r2
Seq :: RE a -> RE a -> RE a -- (r1,r2)
Star :: RE a -> RE a -- r*
deriving Eq

equality :: Eq a => RE a -> RE a -> Bool
intersect :: Eq a => RE a -> RE a -> RE a
contains :: Eq a => RE a -> RE a -> Bool

implemented via symbolic manipulation of regular expressions (no explicit finite automata construction) by adapting Antimirov's regular expression rewriting algorithm via partial derivatives.

The implementation is available via the Haskell platform hackage. Check out the regexpr-symbolic package.

The source code describes some of the technical details. You can also check out an earlier post which considers the specific case of intersection.

1 comment:

111 said...

WoW shares many wow gold of its features with previously launched games. Essentially, you battle with Cheapest wow gold monsters and traverse the countryside, by yourself or as a buy cheap wow gold team, find challenging tasks, and go on to higher Cheap Wow Gold levels as you gain skill and experience. In the course of your journey, you will be gaining new powers that are increased as your skill rating goes up. All the same, in terms of its features and quality, that is a ture stroy for this.WoW is far ahead of all other games of the genre the wow power leveling game undoubtedly is in a league of its own and cheapest wow gold playing it is another experience altogether.
Even though WoW is a wow gold cheap rather complicated game, the controls and interface are done in buy warhammer gold such a way that you don't feel the complexity. A good feature of the game is that it buy wow items does not put off people with lengthy manuals. The instructions cannot be simpler and the pop up tips can help you start playing the game World Of Warcraft Gold immediately. If on the other hand, you need a detailed manual, the instructions are there for you to access. Buy wow gold in this site,good for you ,WoW Gold, BUY WOW GOLD.