"Committed_by_peb"

src/GF/Parsing/MCFG/Naive.hs

@@ -0,0 +1,95 @@
+
+module GF.NewParsing.MCFG.Naive where
+
+
+-- GF modules
+import GF.NewParsing.GeneralChart
+import GF.Formalism.GCFG
+import GF.Formalism.MCFG
+import GF.Formalism.Utilities
+import GF.NewParsing.MCFG.Range
+import GF.Data.SortedList
+import GF.Data.Assoc
+
+{-- Datatypes and types -------------------------------------------------------
+  NChart    : A RedBlackMap with Items and Keys 
+  Item      : The parse Items are either Active or Passive
+  NKey      : One for Active Items, one for Passive and one for Active Items 
+              to convert to Passive
+  DottedRule: (function-name, LHS, [Found in RHS], [To find in RHS]) 
+------------------------------------------------------------------------------}
+
+type NChart   c n l = ParseChart (Item c n l) (NKey c)
+
+data Item     c n l = Active (DottedRule c n) (LinRec c l Range) [RangeRec l]
+	            | Passive (Abstract c n) (RangeRec l)
+	              deriving (Eq, Ord, Show)      
+
+type DottedRule c n = (Abstract c n, [c])
+
+data NKey         c = Act c
+	            | Pass c
+	            | Final
+	              deriving (Eq, Ord, Show)
+
+
+{-- Parsing -------------------------------------------------------------------
+  recognize: 
+  parse    : Builds a chart from the initial agenda, given by prediction, and
+             the inference rules 
+  keyof    : Given an Item returns an appropriate Key for the Chart
+------------------------------------------------------------------------------}
+
+
+parse :: (Ord t, Ord n, Ord c, Ord l) => MCFGrammar c n l t -> [t] 
+      -> SyntaxChart n (c, RangeRec l)
+parse mcfg toks = chart3
+    where chart3 = assocMap (const groupPairs) chart2
+          chart2 = accumAssoc id $ nubsort chart1
+	  chart1 = [ ((cat, rrec), (fun, zip rhs rrecs)) |
+		     Active (Abs cat _Nil fun, rhs) lins rrecs <- chartLookup chart0 Final,
+		     let rrec = makeRangeRec lins ]
+	  chart0 = process mcfg toks
+
+process :: (Ord t, Ord n, Ord c, Ord l) => MCFGrammar c n l t -> [t] -> NChart c n l
+process mcfg toks = buildChart keyof [convert, combine] (predict toks mcfg)
+
+
+keyof :: Item c n l -> NKey c
+keyof (Active (Abs _ (next:_) _, _) _ _) = Act next 
+keyof (Passive (Abs cat _ _) _)          = Pass cat
+keyof _                                  = Final
+
+
+{--Inference rules ------------------------------------------------------------
+  predict: Creates an Active Item of every Rule in the Grammar to give the 
+           initial Agenda
+  combine: Creates an Active Item every time it is possible to combine 
+           an Active Item from the agenda with a Passive Item from the Chart 
+  convert: Active Items with nothing to find are converted to Passive Items
+------------------------------------------------------------------------------}
+
+predict :: (Eq t, Eq c) => [t] -> MCFGrammar c n l t -> [Item c n l]  
+predict toks mcfg = [ Active (abs, []) lins' [] | 
+		      Rule abs (Cnc _ _ lins) <- mcfg,      
+		      lins' <- rangeRestRec toks lins ]
+
+
+combine :: (Ord n, Ord c, Ord l) => NChart c n l -> Item c n l -> [Item c n l]
+combine chart (Active (Abs nt (c:find) f, found) lins rrecs) = 
+    do Passive _ rrec <- chartLookup chart (Pass c)
+       lins' <- concLinRec $ substArgRec (length found) rrec lins
+       return $ Active (Abs nt find f, found ++ [c]) lins' (rrecs ++ [rrec])
+combine chart (Passive (Abs c _ _) rrec) = 
+    do Active (Abs nt (c:find) f, found) lins rrecs <- chartLookup chart (Act c)
+       lins' <- concLinRec $ substArgRec (length found) rrec lins
+       return $ Active (Abs nt find f, found ++ [c]) lins' (rrecs ++ [rrec])
+combine _ _ = []
+
+
+convert :: (Ord n, Ord c, Ord l) => NChart c n l -> Item c n l -> [Item c n l]
+convert _ (Active (Abs nt [] f, rhs) lins _) = [Passive (Abs nt rhs f) rrec]
+    where rrec = makeRangeRec lins
+convert _ _                                  = []
+
+