module Text.RegExp.Matching where
import Data.Semiring
import Text.RegExp.Data
accept :: RegExp c -> [c] -> Bool
accept r = fullMatch r
matchingCount :: Num a => RegExp c -> [c] -> a
matchingCount r = getNumeric . fullMatch r
fullMatch :: Semiring w => RegExp c -> [c] -> w
fullMatch (RegExp r) = matchW r
partialMatch :: Weight c (Int,c) w => RegExp c -> [c] -> w
partialMatch (RegExp r) =
matchW (arb `seqW` weighted r `seqW` arb) . zip [(0::Int)..]
where arb = repW (symW "." (const one))
matchW :: Semiring w => RegW w c -> [c] -> w
matchW r [] = empty r
matchW r (c:cs) = final (foldl (shiftW zero) (shiftW one r c) cs)
shiftW :: Semiring w => w -> RegW w c -> c -> RegW w c
shiftW w r c | active r || w /= zero = shift w (reg r) c
| otherwise = r
shift :: Semiring w => w -> Reg w c -> c -> RegW w c
shift _ Eps _ = epsW
shift w (Sym s f) c = let w' = w .*. f c
in (symW s f) { active = w' /= zero, final_ = w' }
shift w (Alt p q) c = altW (shiftW w p c) (shiftW w q c)
shift w (Seq p q) c = seqW (shiftW w p c)
(shiftW (w .*. empty p .+. final p) q c)
shift w (Rep r) c = repW (shiftW (w .+. final r) r c)