forked from GitHub/gf-core
Completed unoptimized SLF generation.
This commit is contained in:
bringert
@@ -5,9 +5,9 @@
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-- Stability : (stable)
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-- Portability : (portable)
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--
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-- > CVS $Date: 2005/09/08 15:45:17 $
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-- > CVS $Date: 2005/09/12 15:46:44 $
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-- > CVS $Author: bringert $
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-- > CVS $Revision: 1.19 $
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-- > CVS $Revision: 1.20 $
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--
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-- This module does some useful transformations on CFGs.
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--
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@@ -16,12 +16,12 @@
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-- peb thinks: most of this module should be moved to GF.Conversion...
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-----------------------------------------------------------------------------
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module GF.Speech.TransformCFG (CFRule_, CFRules,
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-- FIXME: lots of this stuff is used by CFGToFiniteState, thus
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-- the missing explicit expot list.
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module GF.Speech.TransformCFG {- (CFRule_, CFRules,
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cfgToCFRules, getStartCat,
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removeLeftRecursion,
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removeEmptyCats,
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makeRegular,
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compileAutomaton) where
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removeEmptyCats, removeIdenticalRules) -} where
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import GF.Infra.Ident
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import GF.Formalism.CFG
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@@ -62,8 +62,6 @@ groupProds = fmToList . addListToFM_C (++) emptyFM . map (\r -> (lhsCat r,[r]))
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ungroupProds :: CFRules -> [CFRule_]
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ungroupProds = concat . map snd
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catRules :: CFRules -> Cat_ -> [CFRule_]
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catRules rs c = fromMaybe [] (lookup c rs)
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-- | Remove productions which use categories which have no productions
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removeEmptyCats :: CFRules -> CFRules
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@@ -77,13 +75,18 @@ removeEmptyCats = fix removeEmptyCats'
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emptyCats = filter (nothingOrNull . flip lookup rs) allCats
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k' = map (\ (c,xs) -> (c, filter (not . anyUsedBy emptyCats) xs)) keep
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-- | Remove rules which are identical, not caring about the rule names.
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removeIdenticalRules :: CFRules -> CFRules
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removeIdenticalRules g = [(c,nubBy sameCatAndRhs rs) | (c,rs) <- g]
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where sameCatAndRhs (CFRule c1 ss1 _) (CFRule c2 ss2 _) = c1 == c2 && ss1 == ss2
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removeLeftRecursion :: CFRules -> CFRules
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removeLeftRecursion rs = concatMap removeDirectLeftRecursion $ map handleProds rs
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where
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handleProds (c, r) = (c, concatMap handleProd r)
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handleProd (CFRule ai (Cat aj:alpha) n) | aj < ai =
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-- FIXME: this will give multiple rules with the same name
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[CFRule ai (beta ++ alpha) n | CFRule _ beta _ <- fromJust (lookup aj rs)]
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[CFRule ai (beta ++ alpha) n | CFRule _ beta _ <- lookup' aj rs]
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handleProd r = [r]
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removeDirectLeftRecursion :: (Cat_,[CFRule_]) -- ^ All productions for a category
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@@ -103,92 +106,22 @@ isDirectLeftRecursive (CFRule c (Cat c':_) _) = c == c'
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isDirectLeftRecursive _ = False
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-- Use the transformation algorithm from \"Regular Approximation of Context-free
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-- Grammars through Approximation\", Mohri and Nederhof, 2000
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-- to create an over-generating regular frammar for a context-free
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-- grammar
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makeRegular :: CFRules -> CFRules
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makeRegular g = groupProds $ concatMap trSet (mutRecCats g)
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where trSet cs | allXLinear cs rs = rs
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| otherwise = concatMap handleCat cs
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where rs = concatMap (catRules g) cs
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handleCat c = [CFRule c' [] (mkName (c++"-empty"))] -- introduce A' -> e
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++ concatMap (makeRightLinearRules c) (catRules g c)
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where c' = newCat c
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makeRightLinearRules b' (CFRule c ss n) =
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case ys of
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[] -> [CFRule b' (xs ++ [Cat (newCat c)]) n] -- no non-terminals left
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(Cat b:zs) -> CFRule b' (xs ++ [Cat b]) n
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: makeRightLinearRules (newCat b) (CFRule c zs n)
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where (xs,ys) = break (`catElem` cs) ss
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newCat c = c ++ "$"
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-- | Get the sets of mutually recursive non-terminals for a grammar.
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mutRecCats :: CFRules -> [[Cat_]]
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mutRecCats g = equivalenceClasses $ symmetricSubrelation $ transitiveClosure $ reflexiveClosure allCats r
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where r = nub [(c,c') | (_,rs) <- g, CFRule c ss _ <- rs, Cat c' <- ss]
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allCats = map fst g
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-- Convert a strongly regular grammar to a finite automaton.
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compileAutomaton :: Cat_ -- ^ Start category
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-> CFRules
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-> FA () (Maybe Token)
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compileAutomaton start g = make_fa s [Cat start] f g fa''
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where fa = newFA ()
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s = startState fa
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(fa',f) = newState () fa
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fa'' = addFinalState f fa'
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-- | The make_fa algorithm from \"Regular approximation of CFLs: a grammatical view\",
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-- Mark-Jan Nederhof. International Workshop on Parsing Technologies, 1997.
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make_fa :: State -> [Symbol Cat_ Token] -> State
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-> CFRules -> FA () (Maybe Token) -> FA () (Maybe Token)
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make_fa q0 a q1 g fa =
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case a of
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[] -> newTrans q0 q1 Nothing fa
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[Tok t] -> newTrans q0 q1 (Just t) fa
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[Cat c] -> undefined
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(x:beta) -> let (fa',q) = newState () fa
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fa'' = make_fa q0 [x] q g fa'
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fa''' = make_fa q beta q1 g fa''
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in fa'''
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--
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-- * CFG rule utilities
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--
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{-
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-- | Get all the rules for a given category.
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catRules :: Eq c => [CFRule c n t] -> c -> [CFRule c n t]
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catRules rs c = [r | r@(CFRule c' _ _) <- rs, c' == c]
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-}
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catRules :: CFRules -> Cat_ -> [CFRule_]
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catRules rs c = fromMaybe [] (lookup c rs)
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-- | Gets the set of LHS categories of a set of rules.
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lhsCats :: Eq c => [CFRule c n t] -> [c]
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lhsCats = nub . map lhsCat
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catSetRules :: CFRules -> [Cat_] -> [CFRule_]
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catSetRules g s = concatMap (catRules g) s
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lhsCat :: CFRule c n t -> c
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lhsCat (CFRule c _ _) = c
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-- | Check if all the rules are right-linear, or all the rules are
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-- left-linear, with respect to given categories.
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allXLinear :: Eq c => [c] -> [CFRule c n t] -> Bool
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allXLinear cs rs = all (isRightLinear cs) rs || all (isLeftLinear cs) rs
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ruleRhs :: CFRule c n t -> [Symbol c t]
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ruleRhs (CFRule _ ss _) = ss
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-- | Checks if a context-free rule is right-linear.
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isRightLinear :: Eq c => [c] -- ^ The categories to consider
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-> CFRule c n t -- ^ The rule to check for right-linearity
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-> Bool
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isRightLinear cs (CFRule _ ss _) = all (not . (`catElem` cs)) (safeInit ss)
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-- | Checks if a context-free rule is left-linear.
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isLeftLinear :: Eq c => [c] -- ^ The categories to consider
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-> CFRule c n t -- ^ The rule to check for right-linearity
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-> Bool
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isLeftLinear cs (CFRule _ ss _) = all (not . (`catElem` cs)) (drop 1 ss)
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-- | Checks if a symbol is a non-terminal of one of the given categories.
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catElem :: Eq c => Symbol c t -> [c] -> Bool
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@@ -202,37 +135,14 @@ anyUsedBy cs (CFRule _ ss _) = any (`elem` cs) (filterCats ss)
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mkName :: String -> Name
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mkName n = Name (IC n) []
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--
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-- * Relations
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--
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-- FIXME: these could use a more efficent data structures and algorithms.
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isRelatedTo :: Eq a => [(a,a)] -> a -> a -> Bool
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isRelatedTo r x y = (x,y) `elem` r
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transitiveClosure :: Eq a => [(a,a)] -> [(a,a)]
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transitiveClosure r = fix (\r -> r `union` [ (x,w) | (x,y) <- r, (z,w) <- r, y == z ]) r
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reflexiveClosure :: Eq a => [a] -- ^ The set over which the relation is defined.
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-> [(a,a)] -> [(a,a)]
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reflexiveClosure u r = [(x,x) | x <- u] `union` r
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symmetricSubrelation :: Eq a => [(a,a)] -> [(a,a)]
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symmetricSubrelation r = [p | p@(x,y) <- r, (y,x) `elem` r]
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-- | Get the equivalence classes from an equivalence relation. Since
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-- the relation is relexive, the set can be recoved from the relation.
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equivalenceClasses :: Eq a => [(a,a)] -> [[a]]
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equivalenceClasses r = equivalenceClasses_ (nub (map fst r)) r
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where equivalenceClasses_ [] _ = []
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equivalenceClasses_ (x:xs) r = (x:ys):equivalenceClasses_ zs r
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where (ys,zs) = partition (isRelatedTo r x) xs
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--
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-- * Utilities
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--
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findSet :: Eq c => c -> [[c]] -> Maybe [c]
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findSet x = find (x `elem`)
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fix :: Eq a => (a -> a) -> a -> a
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fix f x = let x' = f x in if x' == x then x else fix f x'
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@@ -240,26 +150,12 @@ nothingOrNull :: Maybe [a] -> Bool
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nothingOrNull Nothing = True
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nothingOrNull (Just xs) = null xs
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safeInit :: [a] -> [a]
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safeInit [] = []
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safeInit xs = init xs
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unionAll :: Eq a => [[a]] -> [a]
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unionAll = nub . concat
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whenMP :: MonadPlus m => Bool -> a -> m a
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whenMP b x = if b then return x else mzero
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--
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-- * Testing stuff, can be removed
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--
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lookup' :: Eq a => a -> [(a,b)] -> b
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lookup' x = fromJust . lookup x
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c --> ss = CFRule c ss (mkName "")
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prGr g = putStrLn $ showGr g
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showGr g = unlines $ map showRule g
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showRule (CFRule c ss _) = c ++ " --> " ++ unwords (map showSym ss)
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showSym s = symbol id show s
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