module CabalGild.Unstable.Type.Optional where

-- | 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.
data Optional a
  = Default
  | Specific a
  deriving (Optional a -> Optional a -> Bool
(Optional a -> Optional a -> Bool)
-> (Optional a -> Optional a -> Bool) -> Eq (Optional a)
forall a. Eq a => Optional a -> Optional a -> Bool
forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
$c== :: forall a. Eq a => Optional a -> Optional a -> Bool
== :: Optional a -> Optional a -> Bool
$c/= :: forall a. Eq a => Optional a -> Optional a -> Bool
/= :: Optional a -> Optional a -> Bool
Eq, Int -> Optional a -> ShowS
[Optional a] -> ShowS
Optional a -> String
(Int -> Optional a -> ShowS)
-> (Optional a -> String)
-> ([Optional a] -> ShowS)
-> Show (Optional a)
forall a. Show a => Int -> Optional a -> ShowS
forall a. Show a => [Optional a] -> ShowS
forall a. Show a => Optional a -> String
forall a.
(Int -> a -> ShowS) -> (a -> String) -> ([a] -> ShowS) -> Show a
$cshowsPrec :: forall a. Show a => Int -> Optional a -> ShowS
showsPrec :: Int -> Optional a -> ShowS
$cshow :: forall a. Show a => Optional a -> String
show :: Optional a -> String
$cshowList :: forall a. Show a => [Optional a] -> ShowS
showList :: [Optional a] -> ShowS
Show)

-- | Converts a 'Maybe' value into an 'Optional' one.
fromMaybe :: Maybe a -> Optional a
fromMaybe :: forall a. Maybe a -> Optional a
fromMaybe = Optional a -> (a -> Optional a) -> Maybe a -> Optional a
forall b a. b -> (a -> b) -> Maybe a -> b
maybe Optional a
forall a. Optional a
Default a -> Optional a
forall a. a -> Optional a
Specific

-- | Converts an 'Optional' value into a 'Maybe' one.
toMaybe :: Optional a -> Maybe a
toMaybe :: forall a. Optional a -> Maybe a
toMaybe Optional a
o = case Optional a
o of
  Optional a
Default -> Maybe a
forall a. Maybe a
Nothing
  Specific a
s -> a -> Maybe a
forall a. a -> Maybe a
Just a
s