Data.Extend

This package allows you to extend a Haskell data like how you do in OOP.

Here is an example use for testing:

data Test = Test | TestA {
      f1 :: Int,
      f2 :: Maybe Int,
      f3 :: Maybe Int
   } deriving (Show, Generic, Eq)

test1A = TestA 1 (Just 1) (Just 3)
test2A = TestA 0 Nothing (Just 2)

main :: IO ()
main = hspec $
   describe "Data.Extend" $ do
      specify "Int" $
         (2 `extend` 1) `shouldBe` (2 :: Int)
      specify "String" $
         ("b" `extend` "a") `shouldBe` "b"
      specify "data 0" $
         (Test `extend` Test) `shouldBe` Test
      specify "data 1" $
         (test2A `extend` test1A) `shouldBe` TestA 0 (Just 1) (Just 2)

Documentation

class Extend a where

Methods

extend :: a -> a -> a

By default

a `extend` b = a

Nothing `extend` Just a = Just a

To use the Extend class, simply make your data derive Generic.

If "a" is a user defined data type, then all Nothing fields of "a" are replaced by corresponding fields in "b",

ie, all Just fields in "a" will override corresponding fields in "b".

extend :: (Generic a, GExtend (Rep a)) => a -> a -> a

By default

a `extend` b = a

Nothing `extend` Just a = Just a

To use the Extend class, simply make your data derive Generic.

If "a" is a user defined data type, then all Nothing fields of "a" are replaced by corresponding fields in "b",

ie, all Just fields in "a" will override corresponding fields in "b".

Instances

Extend a

Methods

extend :: a -> a -> a

Extend a => Extend (Maybe a)

Methods

extend :: Maybe a -> Maybe a -> Maybe a