module Data.DP.Examples.HMM where 
import Data.DP
import Data.Semiring

data HMMState = Start | State Int

states = Start : map State [0..100]

hmmSimple trans (0, Start) = one
hmmSimple trans (i, State curState) = 
    mconcat $ 
         [ f (i-1, trans ) `times` 
           constant (lastState `trans` curState) | 
           lastState <- states] 


hmmCC allTrans 0 = mkCell [mkItem Start one]
hmmCC allTrans i = 
   getCell (i-1) (\(lastState, lastScore) -> 
       mkCell $ [ mkItem (State newState)
                  (lastScore `times` constant score) | 
                 (newState, score) <- allTrans lastState])