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introduce Default1 in a similar way like Eq1, Ord1, etc. #24

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introduce Default1 in a similar way like Eq1, Ord1, etc. #24

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11 changes: 11 additions & 0 deletions data-default-class/Data/Default/Class.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -86,6 +86,17 @@ class Default a where
def = to gdef
#endif

-- | A class to specify that complex type with a default wrapped type,
class Default1 (f :: * -> *) where
liftDef :: a -> f a

-- | Create a default value by making use of the 'Default1' instance
-- and the 'def' function as default for the item(s) wrapped in the object.
def1 :: (Default1 f, Default a)
=> f a -- ^ The default object constructed with the 'Default1' and the 'def'
-- of the wrapped item.
def1 = liftDef def

instance Default Int where def = 0
instance Default Int8 where def = 0
instance Default Int16 where def = 0
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