diff options
Diffstat (limited to 'src/Text/Pandoc/Readers/Odt/Generic/Fallible.hs')
-rw-r--r-- | src/Text/Pandoc/Readers/Odt/Generic/Fallible.hs | 129 |
1 files changed, 0 insertions, 129 deletions
diff --git a/src/Text/Pandoc/Readers/Odt/Generic/Fallible.hs b/src/Text/Pandoc/Readers/Odt/Generic/Fallible.hs index 877443543..4d6a67b8e 100644 --- a/src/Text/Pandoc/Readers/Odt/Generic/Fallible.hs +++ b/src/Text/Pandoc/Readers/Odt/Generic/Fallible.hs @@ -39,10 +39,6 @@ compatible instances of "ArrowChoice". -- We export everything module Text.Pandoc.Readers.Odt.Generic.Fallible where -import Control.Applicative -import Control.Monad - -import qualified Data.Foldable as F import Data.Monoid ((<>)) -- | Default for now. Will probably become a class at some point. @@ -51,16 +47,6 @@ type Failure = () type Fallible a = Either Failure a --- | False -> Left (), True -> Right () -boolToEither :: Bool -> Fallible () -boolToEither False = Left () -boolToEither True = Right () - --- | False -> Left (), True -> Right () -boolToChoice :: Bool -> Fallible () -boolToChoice False = Left () -boolToChoice True = Right () - -- maybeToEither :: Maybe a -> Fallible a maybeToEither (Just a) = Right a @@ -71,21 +57,11 @@ eitherToMaybe :: Either _l a -> Maybe a eitherToMaybe (Left _) = Nothing eitherToMaybe (Right a) = Just a --- | > untagEither === either id id -untagEither :: Either a a -> a -untagEither (Left a) = a -untagEither (Right a) = a - -- | > fromLeft f === either f id fromLeft :: (a -> b) -> Either a b -> b fromLeft f (Left a) = f a fromLeft _ (Right b) = b --- | > fromRight f === either id f -fromRight :: (a -> b) -> Either b a -> b -fromRight _ (Left b) = b -fromRight f (Right a) = f a - -- | > recover a === fromLeft (const a) === either (const a) id recover :: a -> Either _f a -> a recover a (Left _) = a @@ -110,24 +86,6 @@ collapseEither (Left f ) = Left f collapseEither (Right (Left f)) = Left f collapseEither (Right (Right x)) = Right x --- | If either of the values represents an error, the result is a --- (possibly combined) error. If both values represent a success, --- both are returned. -chooseMin :: (Monoid a) => Either a b -> Either a b' -> Either a (b,b') -chooseMin = chooseMinWith (,) - --- | If either of the values represents an error, the result is a --- (possibly combined) error. If both values represent a success, --- a combination is returned. -chooseMinWith :: (Monoid a) => (b -> b' -> c) - -> Either a b - -> Either a b' - -> Either a c -chooseMinWith (><) (Right a) (Right b) = Right $ a >< b -chooseMinWith _ (Left a) (Left b) = Left $ a <> b -chooseMinWith _ (Left a) _ = Left a -chooseMinWith _ _ (Left b) = Left b - -- | If either of the values represents a non-error, the result is a -- (possibly combined) non-error. If both values represent an error, an error -- is returned. @@ -152,87 +110,11 @@ chooseMaxWith _ _ (Right b) = Right b class ChoiceVector v where spreadChoice :: v (Either f a) -> Either f (v a) --- Let's do a few examples first - -instance ChoiceVector Maybe where - spreadChoice (Just (Left f)) = Left f - spreadChoice (Just (Right x)) = Right (Just x) - spreadChoice Nothing = Right Nothing - -instance ChoiceVector (Either l) where - spreadChoice (Right (Left f)) = Left f - spreadChoice (Right (Right x)) = Right (Right x) - spreadChoice (Left x ) = Right (Left x) - instance ChoiceVector ((,) a) where spreadChoice (_, Left f) = Left f spreadChoice (x, Right y) = Right (x,y) -- Wasn't there a newtype somewhere with the elements flipped? --- --- More instances later, first some discussion. --- --- I'll have to freshen up on type system details to see how (or if) to do --- something like --- --- > instance (ChoiceVector a, ChoiceVector b) => ChoiceVector (a b) where --- > : --- --- But maybe it would be even better to use something like --- --- > class ChoiceVector v v' f | v -> v' f where --- > spreadChoice :: v -> Either f v' --- --- That way, more places in @v@ could spread the cheer, e.g.: --- --- As before: --- -- ( a , Either f b) (a , b) f --- > instance ChoiceVector ((,) a (Either f b)) ((,) a b) f where --- > spreadChoice (_, Left f) = Left f --- > spreadChoice (a, Right b) = Right (a,b) --- --- But also: --- -- ( Either f a , b) (a , b) f --- > instance ChoiceVector ((,) (Either f a) b) ((,) a b) f where --- > spreadChoice (Right a,b) = Right (a,b) --- > spreadChoice (Left f,_) = Left f --- --- And maybe even: --- -- ( Either f a , Either f b) (a , b) f --- > instance ChoiceVector ((,) (Either f a) (Either f b)) ((,) a b) f where --- > spreadChoice (Right a , Right b) = Right (a,b) --- > spreadChoice (Left f , _ ) = Left f --- > spreadChoice ( _ , Left f) = Left f --- --- Of course that would lead to a lot of overlapping instances... --- But I can't think of a different way. A selector function might help, --- but not even a "Data.Traversable" is powerful enough for that. --- But maybe someone has already solved all this with a lens library. --- --- Well, it's an interesting academic question. But for practical purposes, --- I have more than enough right now. - -instance ChoiceVector ((,,) a b) where - spreadChoice (_,_, Left f) = Left f - spreadChoice (a,b, Right x) = Right (a,b,x) - -instance ChoiceVector ((,,,) a b c) where - spreadChoice (_,_,_, Left f) = Left f - spreadChoice (a,b,c, Right x) = Right (a,b,c,x) - -instance ChoiceVector ((,,,,) a b c d) where - spreadChoice (_,_,_,_, Left f) = Left f - spreadChoice (a,b,c,d, Right x) = Right (a,b,c,d,x) - -instance ChoiceVector (Const a) where - spreadChoice (Const c) = Right (Const c) -- need to repackage because of implicit types - --- | Fails on the first error -instance ChoiceVector [] where - spreadChoice = sequence -- using the monad instance of Either. - -- Could be generalized to "Data.Traversable" - but why play - -- with UndecidableInstances unless this is really needed. - -- | Wrapper for a list. While the normal list instance of 'ChoiceVector' -- fails whenever it can, this type will never fail. newtype SuccessList a = SuccessList { collectNonFailing :: [a] } @@ -247,14 +129,3 @@ instance ChoiceVector SuccessList where collectRights :: [Either _l r] -> [r] collectRights = collectNonFailing . untag . spreadChoice . SuccessList where untag = fromLeft (error "Unexpected Left") - --- | A version of 'collectRights' generalized to other containers. The --- container must be both "reducible" and "buildable". Most general containers --- should fullfill these requirements, but there is no single typeclass --- (that I know of) for that. --- Therefore, they are split between 'Foldable' and 'MonadPlus'. --- (Note that 'Data.Traversable.Traversable' alone would not be enough, either.) -collectRightsF :: (F.Foldable c, MonadPlus c) => c (Either _l r) -> c r -collectRightsF = F.foldr unTagRight mzero - where unTagRight (Right x) = mplus $ return x - unTagRight _ = id |