[Haskell-beginners] basic use of Applicative

[Imants Cekusins]

-- (a::Int -> b::Bool)

module ApplicativeAb where


-- 2 arg
add3:: Int -> Bool -> Int
add3 x1 addYes
   | addYes = x1 + 3
   | otherwise = x1


main::IO()
main =   do
   print $  maybe2 (Just 3) (Just True)
   print $  maybe2 (Just 3) (Just False)
   print $  list2 [3] [True]


-- maybe
maybe2::Maybe Int -> Maybe Bool -> Maybe Int
maybe2 mi mb = add3 <$> mi <*> mb


-- list
list2::[Int] -> [Bool] -> [Int]
list2 i b = add3 <$> i <*> b