module Text.RegExp.Matching.Leftmost.Type where
import Data.Semiring
import Text.RegExp.Data
data Leftmost = Zero | One | Leftmost !Int
deriving (Eq,Show)
instance Semiring Leftmost where
zero = Zero; one = One
Zero .+. y = y
x .+. Zero = x
One .+. y = y
x .+. One = x
Leftmost a .+. Leftmost b = Leftmost (min a b)
Zero .*. _ = Zero
_ .*. Zero = Zero
One .*. y = y
x .*. One = x
Leftmost a .*. Leftmost b = Leftmost (min a b)
instance Weight c (Int,c) Leftmost where
symWeight p (n,c) = p c .*. Leftmost n