Fix issue 61: GF shell cannot parse a system command ending with a space

Trailing spaces caused the command line parse to be ambiguous, and
ambiguous parses were rejected by function readCommandLine, causing
the cryptic error message "command not parsed".

src/compiler/GF/Command/Parse.hs

@@ -1,63 +1,65 @@
 module GF.Command.Parse(readCommandLine, pCommand) where
 
-import PGF
+import PGF(pExpr,pIdent)
 import GF.Command.Abstract
 
-import Data.Char
-import Control.Monad
-import qualified Text.ParserCombinators.ReadP as RP
+import Data.Char(isDigit,isSpace)
+import Control.Monad(liftM2)
+import Text.ParserCombinators.ReadP
 
 readCommandLine :: String -> Maybe CommandLine
-readCommandLine s = case [x | (x,cs) <- RP.readP_to_S pCommandLine s, all isSpace cs] of
-                      [x] -> Just x
-                      _   -> Nothing
+readCommandLine s =
+    case [x | (x,cs) <- readP_to_S pCommandLine s, all isSpace cs] of
+      [x] -> Just x
+      _   -> Nothing
 
 pCommandLine =
-  (RP.skipSpaces >> RP.char '-' >> RP.char '-' >> RP.skipMany (RP.satisfy (const True)) >> return [])   -- comment
-  RP.<++
-  (RP.sepBy (RP.skipSpaces >> pPipe) (RP.skipSpaces >> RP.char ';'))
+  (skipSpaces >> char '-' >> char '-' >> pTheRest >> return [])   -- comment
+  <++
+  (sepBy (skipSpaces >> pPipe) (skipSpaces >> char ';'))
 
-pPipe = RP.sepBy1 (RP.skipSpaces >> pCommand) (RP.skipSpaces >> RP.char '|')
+pPipe = sepBy1 (skipSpaces >> pCommand) (skipSpaces >> char '|')
 
 pCommand = (do
-  cmd  <- pIdent RP.<++ (RP.char '%' >> pIdent >>= return . ('%':))
-  RP.skipSpaces
-  opts <- RP.sepBy pOption RP.skipSpaces
+  cmd  <- pIdent <++ (char '%' >> pIdent >>= return . ('%':))
+  skipSpaces
+  opts <- sepBy pOption skipSpaces
   arg  <- pArgument
   return (Command cmd opts arg)
   )
-    RP.<++ (do
-  RP.char '?' 
-  c <- pSystemCommand 
+    <++ (do
+  char '?'
+  skipSpaces
+  c <- pSystemCommand
   return (Command "sp" [OFlag "command" (VStr c)] ANoArg)
-  ) 
+  )
 
 pOption = do
-  RP.char '-'
+  char '-'
   flg <- pIdent
-  RP.option (OOpt flg) (fmap (OFlag flg) (RP.char '=' >> pValue))
+  option (OOpt flg) (fmap (OFlag flg) (char '=' >> pValue))
 
 pValue = do
-  fmap VInt (RP.readS_to_P reads)
-  RP.<++
-  fmap VStr (RP.readS_to_P reads)
-  RP.<++
+  fmap VInt (readS_to_P reads)
+  <++
+  fmap VStr (readS_to_P reads)
+  <++
   fmap VId  pFilename
 
-pFilename = liftM2 (:) (RP.satisfy isFileFirst) (RP.munch (not . isSpace)) where
+pFilename = liftM2 (:) (satisfy isFileFirst) (munch (not . isSpace)) where
   isFileFirst c = not (isSpace c) && not (isDigit c)
 
-pArgument =          
-  RP.option ANoArg 
+pArgument =
+  option ANoArg
     (fmap AExpr pExpr
-              RP.<++ 
-    (RP.munch isSpace >> RP.char '%' >> fmap AMacro pIdent))
+              <++
+    (skipSpaces >> char '%' >> fmap AMacro pIdent))
 
-pSystemCommand = 
-  RP.munch isSpace >> (
-    (RP.char '"' >> (RP.manyTill (pEsc RP.<++ RP.get) (RP.char '"')))
-      RP.<++
-    RP.many RP.get
-    )
-       where
-         pEsc = RP.char '\\' >> RP.get 
+pSystemCommand =
+    (char '"' >> (manyTill (pEsc <++ get) (char '"')))
+      <++
+    pTheRest
+  where
+    pEsc = char '\\' >> get
+
+pTheRest = munch (const True)