Founding the newly structured GF2.0 cvs archive.

src/GF/CF/CF.hs

@@ -0,0 +1,180 @@
+module CF where
+
+import Operations
+import Str
+import AbsGFC
+import GFC
+import CFIdent
+import List (nub,nubBy)
+import Char (isUpper, isLower, toUpper, toLower)
+
+-- context-free grammars. AR 15/12/1999 -- 30/3/2000 -- 2/6/2001 -- 3/12/2001
+
+-- CF grammar data types
+
+-- abstract type CF. 
+-- Invariant: each category has all its rules grouped with it 
+--      also: the list is never empty (the category is just missing then)
+newtype CF  = CF ([(CFCat,[CFRule])], CFPredef) 
+type CFRule = (CFFun, (CFCat, [CFItem]))
+
+-- CFPredef is a hack for variable symbols and literals; normally = const []
+data CFItem = CFTerm RegExp | CFNonterm CFCat deriving (Eq, Ord,Show)
+
+newtype CFTree = CFTree (CFFun,(CFCat, [CFTree])) deriving (Eq, Show)
+
+type CFPredef  = CFTok -> [(CFCat, CFFun)] -- recognize literals, variables, etc
+
+-- Wadler style + return information
+type CFParser = [CFTok] -> ([(CFTree,[CFTok])],String)
+
+cfParseResults :: ([(CFTree,[CFTok])],String) -> [CFTree]
+cfParseResults rs = [b | (b,[]) <- fst rs]
+
+-- terminals are regular expressions on words; to be completed to full regexp
+data RegExp = 
+    RegAlts [CFWord]         -- list of alternative words
+  | RegSpec CFTok            -- special token
+  deriving (Eq, Ord, Show)
+
+type CFWord = String
+
+-- the above types should be kept abstract, and the following functions used
+
+-- to construct CF grammars
+
+emptyCF :: CF
+emptyCF = CF ([], emptyCFPredef)
+
+emptyCFPredef :: CFPredef
+emptyCFPredef = const []
+
+rules2CF :: [CFRule] -> CF
+rules2CF rs = CF (groupCFRules rs, emptyCFPredef)
+
+groupCFRules :: [CFRule] -> [(CFCat,[CFRule])]
+groupCFRules = foldr ins [] where
+  ins rule crs = case crs of
+    (c,r) : rs | compatCF c cat -> (c,rule:r) : rs
+    cr    : rs            -> cr         : ins rule rs
+    _                     -> [(cat,[rule])]
+   where
+     cat = valCatCF rule
+
+-- to construct rules
+
+-- make a rule from a single token without constituents
+atomCFRule :: CFCat -> CFFun -> CFTok -> CFRule
+atomCFRule c f s = (f, (c, [atomCFTerm s]))
+
+-- usual terminal
+atomCFTerm :: CFTok -> CFItem 
+atomCFTerm = CFTerm . atomRegExp
+
+atomRegExp :: CFTok -> RegExp
+atomRegExp t = case t of
+  TS s -> RegAlts [s] 
+  _    -> RegSpec t
+
+-- terminal consisting of alternatives
+altsCFTerm :: [String] -> CFItem 
+altsCFTerm = CFTerm . RegAlts
+
+
+-- to construct trees
+
+-- make a tree without constituents
+atomCFTree :: CFCat -> CFFun -> CFTree
+atomCFTree c f = buildCFTree c f []
+
+-- make a tree with constituents. 
+buildCFTree :: CFCat -> CFFun -> [CFTree] -> CFTree
+buildCFTree c f trees = CFTree (f,(c,trees))
+
+{- ----
+cfMeta0 :: CFTree
+cfMeta0 = atomCFTree uCFCat metaCFFun
+
+-- used in happy
+litCFTree :: String -> CFTree --- Maybe CFTree
+litCFTree s = maybe cfMeta0 id $ do
+  (c,f) <- getCFLiteral s
+  return $ buildCFTree c f []
+-}
+
+-- to decide whether a token matches a terminal item
+
+matchCFTerm :: CFItem -> CFTok -> Bool
+matchCFTerm (CFTerm t) s = satRegExp t s
+matchCFTerm _ _ = False
+
+satRegExp :: RegExp -> CFTok -> Bool
+satRegExp r t = case (r,t) of 
+  (RegAlts tt, TS s) -> elem s tt
+  (RegAlts tt, TC s) -> or [elem s' tt | s' <- caseUpperOrLower s]
+  (RegSpec x,  _)    -> t == x ---
+  _ -> False
+ where
+   caseUpperOrLower s = case s of
+     c:cs | isUpper c -> [s, toLower c : cs]
+     c:cs | isLower c -> [s, toUpper c : cs]
+     _ -> [s]
+
+-- to analyse a CF grammar
+
+catsOfCF :: CF -> [CFCat]
+catsOfCF (CF (rr,_)) = map fst rr 
+
+rulesOfCF :: CF -> [CFRule]
+rulesOfCF (CF (rr,_)) = concatMap snd rr
+
+ruleGroupsOfCF :: CF -> [(CFCat,[CFRule])]
+ruleGroupsOfCF (CF (rr,_)) = rr
+
+rulesForCFCat :: CF -> CFCat -> [CFRule]
+rulesForCFCat (CF (rr,_)) cat = maybe [] id $ lookup cat rr
+
+valCatCF :: CFRule -> CFCat
+valCatCF (_,(c,_)) = c
+
+valItemsCF :: CFRule -> [CFItem]
+valItemsCF (_,(_,i)) = i
+
+valFunCF :: CFRule -> CFFun
+valFunCF  (f,(_,_)) = f
+
+startCat :: CF -> CFCat
+startCat (CF (rr,_)) = fst (head rr) --- hardly useful
+
+predefOfCF :: CF -> CFPredef
+predefOfCF (CF (_,f)) = f
+
+appCFPredef :: CF -> CFTok -> [(CFCat, CFFun)]
+appCFPredef = ($) . predefOfCF
+
+valCFItem :: CFItem -> Either RegExp CFCat
+valCFItem (CFTerm r)     = Left r
+valCFItem (CFNonterm nt) = Right nt
+
+cfTokens :: CF -> [CFWord]
+cfTokens cf = nub $ concat $ [ wordsOfRegExp i | r <- rulesOfCF cf, 
+                                                 CFTerm i <- valItemsCF r]
+
+wordsOfRegExp :: RegExp -> [CFWord]
+wordsOfRegExp (RegAlts tt) = tt
+wordsOfRegExp _ = []
+
+forCFItem :: CFTok -> CFRule -> Bool
+forCFItem a (_,(_, CFTerm r : _)) = satRegExp r a
+forCFItem _ _ = False
+
+isCircularCF :: CFRule -> Bool
+isCircularCF (_,(c', CFNonterm c:[])) = compatCF c' c
+isCircularCF _ = False
+--- we should make a test of circular chains, too
+
+-- coercion to the older predef cf type
+
+predefRules :: CFPredef -> CFTok -> [CFRule]
+predefRules pre s = [atomCFRule c f s | (c,f) <- pre s]
+