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Constant-time length and indexing of input lists.

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This commit is contained in:
Rob Rix 2016-06-06 23:03:32 -04:00
parent 65064d03de
commit 0061d075f2
1 changed files with 3 additions and 1 deletions
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4
src/SES.hs
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@ -3,6 +3,7 @@ module SES where
import Control.Parallel.Strategies
import Data.List ((!!))
import qualified Data.Map as Map
import qualified Data.Vector as Vector
import Patch
import Prologue
import Unsafe
@ -53,7 +54,8 @@ diffAt diffTerms cost (i, j) as bs
ses' :: Applicative edit => Compare term (edit (Patch term)) -> Cost (edit (Patch term)) -> [term] -> [term] -> [edit (Patch term)]
ses' diffTerms cost as bs = fst <$> diffAtMemo 0 0
where diffAtMemo = fix (memoize2d (length as) (length bs) . diffAt' diffTerms cost (index as) (index bs))
index elements i = if i < length elements then Just (elements !! i) else Nothing
index list i = if i < length elements then Just (elements Vector.! i) else Nothing
where elements = Vector.fromList list
diffAt' :: Applicative edit => Compare term (edit (Patch term)) -> Cost (edit (Patch term)) -> (Int -> Maybe term) -> (Int -> Maybe term) -> (Int -> Int -> [(edit (Patch term), Integer)]) -> Int -> Int -> [(edit (Patch term), Integer)]
diffAt' diffTerms cost as bs recur i j