Files
gf-core/src/GF/Parsing/GeneralChart.hs
2005-03-21 21:31:43 +00:00

87 lines
3.0 KiB
Haskell

----------------------------------------------------------------------
-- |
-- Module : GeneralChart
-- Maintainer : Peter Ljunglöf
-- Stability : (stable)
-- Portability : (portable)
--
-- > CVS $Date: 2005/03/21 22:31:48 $
-- > CVS $Author: peb $
-- > CVS $Revision: 1.2 $
--
-- Simple implementation of deductive chart parsing
-----------------------------------------------------------------------------
module GF.Parsing.GeneralChart
(-- * Type definition
Chart,
-- * Main functions
chartLookup,
buildChart,
-- * Probably not needed
emptyChart,
chartMember,
chartInsert,
chartList,
addToChart
) where
-- import Trace
import GF.Data.RedBlackSet
-- main functions
chartLookup :: (Ord item, Ord key) => Chart item key -> key -> [item]
buildChart :: (Ord item, Ord key) => (item -> key) ->
[Chart item key -> item -> [item]] -> [item] -> [item]
buildChart keyof rules axioms = chartList (addItems axioms emptyChart)
where addItems [] = id
addItems (item:items) = addItems items . addItem item
-- addItem item | trace ("+ "++show item++"\n") False = undefined
addItem item = addToChart item (keyof item)
(\chart -> foldr (consequence item) chart rules)
consequence item rule chart = addItems (rule chart item) chart
-- probably not needed
emptyChart :: (Ord item, Ord key) => Chart item key
chartMember :: (Ord item, Ord key) => Chart item key -> item -> key -> Bool
chartInsert :: (Ord item, Ord key) => Chart item key -> item -> key -> Maybe (Chart item key)
chartList :: (Ord item, Ord key) => Chart item key -> [item]
addToChart :: (Ord item, Ord key) => item -> key -> (Chart item key -> Chart item key) -> Chart item key -> Chart item key
addToChart item key after chart = maybe chart after (chartInsert chart item key)
--------------------------------------------------------------------------------
-- key charts as red/black trees
newtype Chart item key = KC (RedBlackMap key item)
deriving Show
emptyChart = KC rbmEmpty
chartMember (KC tree) item key = rbmElem key item tree
chartInsert (KC tree) item key = fmap KC (rbmInsert key item tree)
chartLookup (KC tree) key = rbmLookup key tree
chartList (KC tree) = concatMap snd (rbmList tree)
--------------------------------------------------------------------------------}
{--------------------------------------------------------------------------------
-- key charts as unsorted association lists -- OBSOLETE!
newtype Chart item key = SC [(key, item)]
emptyChart = SC []
chartMember (SC chart) item key = (key,item) `elem` chart
chartInsert (SC chart) item key = if (key,item) `elem` chart then Nothing else Just (SC ((key,item):chart))
chartLookup (SC chart) key = [ item | (key',item) <- chart, key == key' ]
chartList (SC chart) = map snd chart
--------------------------------------------------------------------------------}