Fixed zealous use of `fail` and exported encodeOne in General module

Data/SCargot/General.hs

@@ -16,6 +16,7 @@ module Data.SCargot.General
   , decode
   , decodeOne
   , encode
+  , encodeOne
     -- * Useful Type Aliases
   , Reader
   , Comment

Data/SCargot/Repr/WellFormed.hs

@@ -45,46 +45,46 @@ type Parse t a = R.WellFormedSExpr t -> Either String a
 -- | Utility function for parsing a pair of things.
 fromPair :: Parse t a -> Parse t b -> Parse t (a, b)
 fromPair pl pr (L [l, r]) = (,) <$> pl l <*> pr r
-fromPair _  _  sx = fail ("Expected two-element list")
+fromPair _  _  sx = Left ("Expected two-element list")
 
 -- | Utility function for parsing a list of things.
 fromList :: Parse t a -> Parse t [a]
 fromList p (L ss) = mapM p ss
-fromList _ sx     = fail ("Expected list")
+fromList _ sx     = Left ("Expected list")
 
 fromAtom :: Parse t t
-fromAtom (L _) = fail "Expected atom; found list"
+fromAtom (L _) = Left "Expected atom; found list"
 fromAtom (A a) = return a
 
 asPair :: ((S t, S t) -> Either String a) -> S t -> Either String a
 asPair f (L [l, r]) = f (l, r)
-asPair _ sx         = fail ("Expected two-element list")
+asPair _ sx         = Left ("Expected two-element list")
 
 asList :: ([S t] -> Either String a) -> S t -> Either String a
 asList f (L ls) = f ls
-asList _ sx     = fail ("Expected list")
+asList _ sx     = Left ("Expected list")
 
 isAtom :: Eq t => t -> S t -> Either String ()
 isAtom s (A s')
   | s == s'   = return ()
-  | otherwise = fail ".."
-isAtom _ _  = fail ".."
+  | otherwise = Left ".."
+isAtom _ _  = Left ".."
 
 asAtom :: Show t => (t -> Either String a) -> S t -> Either String a
 asAtom f (A s) = f s
-asAtom _ sx    = fail ("Expected atom; got" ++ show sx)
+asAtom _ sx    = Left ("Expected atom; got" ++ show sx)
 
 asAssoc :: Show t => ([(S t, S t)] -> Either String a) -> S t -> Either String a
 asAssoc f (L ss) = gatherPairs ss >>= f
   where gatherPairs (L [a, b] : ss) = (:) <$> pure (a, b) <*> gatherPairs ss
         gatherPairs []              = pure []
-        gatherPairs _               = fail "..."
-asAssoc _ sx     = fail ("Expected assoc list; got " ++ show sx)
+        gatherPairs _               = Left "..."
+asAssoc _ sx     = Left ("Expected assoc list; got " ++ show sx)
 
 car :: (S t -> Either String t') -> [S t] -> Either String t'
 car f (x:_) = f x
-car _ []    = fail "car: Taking car of zero-element list"
+car _ []    = Left "car: Taking car of zero-element list"
 
 cdr :: ([S t] -> Either String t') -> [S t] -> Either String t'
 cdr f (_:xs) = f xs
-cdr _ []     = fail "cdr: Taking cdr of zero-element list"
+cdr _ []     = Left "cdr: Taking cdr of zero-element list"