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Remove unused sub-networks when generating multiple FAs.

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bringert
2006-01-05 17:46:30 +00:00
parent 6958b7bb7b
commit af905434a2
3 changed files with 40 additions and 11 deletions
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14
src/GF/Speech/CFGToFiniteState.hs
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@@ -150,11 +150,11 @@ data MFALabel a = MFASym a | MFASub String
data MFA a = MFA (DFA (MFALabel a)) [(String,DFA (MFALabel a))]
--
-- * Compile strongly regular grammars to multiple DFAs
-- * Compile a strongly regular grammar to a DFA with sub-automata
--
cfgToMFA :: Options -> CGrammar -> MFA String
cfgToMFA opts g = MFA startFA [(c, toMFA (minimize fa)) | (c,fa) <- fas]
cfgToMFA opts g = removeUnusedSubLats mfa
where start = getStartCat opts
startFA = let (fa,s,f) = newFA_
in newTransition s f (MFASub start) fa
@@ -162,6 +162,16 @@ cfgToMFA opts g = MFA startFA [(c, toMFA (minimize fa)) | (c,fa) <- fas]
mkMFALabel (Cat c) = MFASub c
mkMFALabel (Tok t) = MFASym t
toMFA = mapTransitions mkMFALabel
mfa = MFA startFA [(c, toMFA (minimize fa)) | (c,fa) <- fas]
removeUnusedSubLats :: MFA a -> MFA a
removeUnusedSubLats (MFA main subs) = MFA main [(c,s) | (c,s) <- subs, isUsed c]
where
usedMap = Map.fromList [(c,usedSubLats n) | (c,n) <- subs]
used = growUsedSet (usedSubLats main)
isUsed c = c `Set.member` used
growUsedSet = fix (\s -> foldl Set.union s $ mapMaybe (flip Map.lookup usedMap) $ Set.toList s)
usedSubLats fa = Set.fromList [s | (_,_,MFASub s) <- transitions fa]
-- | Convert a strongly regular grammar to a number of finite automata,
-- one for each non-terminal.