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1. isFieldMaybe :: FieldDef -> Bool

   hledger-web	Hledger.Web.Import

   Check if the field is `Maybe a`

2. intCastMaybe :: (Integral a, Integral b, Bits a, Bits b) => a -> Maybe b

   int-cast	Data.IntCast

   Run-time-checked integer conversion This is an optimized version of the following generic code below

   intCastMaybeRef :: (Integral a, Integral b) => a -> Maybe b
   intCastMaybeRef x
   | toInteger x == toInteger y = Just y
   | otherwise                  = Nothing
   where
   y = fromIntegral x
   

   The code above is rather inefficient as it needs to go via the Integer type. The function intCastMaybe, however, is marked INLINEABLE and if both integral types are statically known, GHC will be able optimize the code signficantly (for -O1 and better). For instance (as of GHC 7.8.1) the following definitions

   w16_to_i32 = intCastMaybe :: Word16 -> Maybe Int32
   
   i16_to_w16 = intCastMaybe :: Int16 -> Maybe Word16
   

   are translated into the following (simplified) GHC Core language

   w16_to_i32 = \x -> Just (case x of _ { W16# x# -> I32# (word2Int# x#) })
   
   i16_to_w16 = \x -> case eta of _
   { I16# b1 -> case tagToEnum# (<=# 0 b1) of _
   { False -> Nothing
   ; True -> Just (W16# (narrow16Word# (int2Word# b1)))
   }
   }
   

   Note: Starting with base-4.8, this function has been added to Data.Bits under the name toIntegralSized.

3. mapMaybeI :: Monoidal f => (a -> f (Maybe b)) -> [a] -> f [b]

   invertible	Control.Invertible.Monoidal

   Map each element to a Maybe monoidal and sequence the results (like traverse and mapMaybe).

4. sequenceMaybesI :: Monoidal f => [f (Maybe a)] -> f [a]

   invertible	Control.Invertible.Monoidal

   Sequence (like sequenceA) and filter (like catMaybes) a list of monoidals, producing the list of non-Nothing values. Shorter input lists pad with Nothings and longer ones are ignored.

5. consMaybe :: (Maybe a, [a]) <-> [a]

   invertible	Data.Invertible.List

   Convert between (Just head, tail) and the non-empty list head:tail, or (Nothing, list) and list.

6. fromMaybe :: Eq a => a -> Maybe a <-> a

   invertible	Data.Invertible.Maybe

   Convert between Nothing and a default value, or Just and its value (not a true bijection).

7. listToMaybe :: [a] <-> Maybe a

   invertible	Data.Invertible.Maybe

   Convert between (the head of) a (singleton) list and Maybe (see listToMaybe). (invert maybeToList)

8. lookupBaseMaybe :: ParseYamlFile a => BaseDir -> Object -> Text -> Parser (Maybe a)

   keter	Keter.Yaml.FilePath

   A replacement for the .:? operator which will both parse a file path and apply the relative file logic.

9. satisfyMaybe :: (FromServerMessage -> Maybe a) -> Session a

   lsp-test	Language.LSP.Test

   Consumes and returns the result of the specified predicate if it returns Just.

10. getMaybeBij :: MaybeBij -> Maybe Bij

    mappings	Data.Bijection

    No documentation available.

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