Safe Haskell	Safe-Inferred
Language	Haskell2010

CabalGild.Type.Optional

Synopsis

data Optional a
- = Default
- | Specific a
withDefault :: a -> Optional a -> a
optional :: b -> (a -> b) -> Optional a -> b

Documentation

data Optional a Source #

Represents a value that may or may not be present. Isomorphic to Maybe. Useful to distinguish between a value not being given and a value happening to be the same as the default.

Constructors

Default
Specific a

Instances

Instances details

Show a => Show (Optional a) Source #
Instance details Defined in CabalGild.Type.Optional Methods showsPrec :: Int -> Optional a -> ShowS # show :: Optional a -> String # showList :: [Optional a] -> ShowS #
Eq a => Eq (Optional a) Source #
Instance details Defined in CabalGild.Type.Optional Methods (==) :: Optional a -> Optional a -> Bool # (/=) :: Optional a -> Optional a -> Bool #

withDefault :: a -> Optional a -> a Source #

Uses the provided default value if the optional is Default, otherwise gets the value out of the Specific. Similar to fromMaybe.

optional :: b -> (a -> b) -> Optional a -> b Source #

Basic destructor, similar to maybe.