command option ma -known to drop unknown words

src/compiler/GF/Command/Commands.hs

@@ -521,6 +521,10 @@ allCommands env@(pgf, mos) = Map.fromList [
                     return . fromString . unwords .
                     morphoMissing (optMorpho opts) . 
                     concatMap words . toStrings
+               _ | isOpt "known" opts ->
+                    return . fromString . unwords .
+                    morphoKnown (optMorpho opts) . 
+                    concatMap words . toStrings
                _ -> return . fromString . unlines . 
                     map prMorphoAnalysis . concatMap (morphos opts) . 
                     concatMap words . toStrings ,
@@ -528,7 +532,8 @@ allCommands env@(pgf, mos) = Map.fromList [
        ("lang","the languages of analysis (comma-separated, no spaces)")
        ],
      options = [
-       ("missing","show the list of unknown words in the input")
+       ("known",  "return only the known words, in order of appearance"),
+       ("missing","show the list of unknown words, in order of appearance")
        ]
      }),
 

src/runtime/haskell/PGF/Morphology.hs

@@ -1,7 +1,8 @@
 module PGF.Morphology(Lemma,Analysis,Morpho,
                       buildMorpho,isInMorpho,
                       lookupMorpho,fullFormLexicon,
-                      morphoMissing,missingWordMsg) where
+                      morphoMissing,morphoKnown,morphoClassify,
+                      missingWordMsg) where
 
 import PGF.CId
 import PGF.Data
@@ -48,8 +49,14 @@ isInMorpho (Morpho mo) s = maybe False (const True) $ Map.lookup s mo
 fullFormLexicon :: Morpho -> [(String,[(Lemma,Analysis)])]
 fullFormLexicon (Morpho mo) = Map.toList mo
 
-morphoMissing :: Morpho -> [String] -> [String]
-morphoMissing mo ws = [w | w <- ws, null (lookupMorpho mo w), notLiteral w] where
+morphoMissing  :: Morpho -> [String] -> [String]
+morphoMissing = morphoClassify False
+
+morphoKnown    :: Morpho -> [String] -> [String]
+morphoKnown = morphoClassify True
+
+morphoClassify :: Bool -> Morpho -> [String] -> [String]
+morphoClassify k mo ws = [w | w <- ws, k /= null (lookupMorpho mo w), notLiteral w] where
   notLiteral w = not (all isDigit w) ---- should be defined somewhere
 
 missingWordMsg :: Morpho -> [String] -> String