Re: [Haskell-cafe] Disjunctive Normal Form

On 11/2/07, Luke Palmer wrote:

On 11/1/07, Arnar Birgisson wrote:

...

dnf :: LS -> DNF dnf (Var s) = [[Pos s]] dnf (Or l1 l2) = (dnf l1) ++ (dnf l2) dnf (And l1 l2) = [t1 ++ t2 | t1 <- dnf l1, t2 <- dnf l2] dnf (Not (Not d)) = dnf d dnf (Not (And l1 l2)) = (dnf $ Not l1) ++ (dnf $ Not l2) dnf (Not (Or l1 l2)) = [t1 ++ t2 | t1 <- dnf $ Not l1, t2 <- dnf $ Not l2]

These two are doing a little extra work:

dnf (Not (And l1 l2)) = dnf (Or (Not l1) (Not l2)) dnf (Not (Or l1 l2)) = dnf (And (Not l1) (Not l2))

I should clarify. I meant that *you* were doing a little extra work, by re-implementing that logic for the not cases. I'm a fan of only implementing each "unit" of logic in one place, whatever that means. But to appease the pedantic, my versions are actually doing more computational work: they are doing one extra pattern match when these patterns are encountered. Whoopty-doo. :-) Luke