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Applicative
In Software Development, this refers to a Functor that provides a method for applying a function wrapped in such a type to a value wrapped in the same type.
In Haskell, the function for applying a wrapped function to a value wrapped in
the same type is available as the infix operator <*>, and facilitates the
application of a function taking an arbitrary number of arguments over multiple
wrapped values. An applicative must also implement the pure function, which
takes a single argument and returns it wrapped.
pure :: Applicative f => a -> f a
(<*>) :: Applicative f => f (a -> b) -> f a -> f b
In the following example, fmap (<$>) first applies the add function to the
value Just 1, resulting in a function of the type Just (Int -> Int). The
applicative infix operator (<*>) then applies that function to the remaining
value Just 2, resulting in Just 3.
add :: Int -> Int -> Int
add x y = x + y
add <$> Just 1 <*> Just 2Prelude> Just 3