Generalizes [[Functor#map|map]] to [[Functions|functions]] with 2+ arguments; lifting functions `a -> b -> c` to `f a -> f b -> f c`

```haskell
class Functor f <= Apply f where
  apply :: forall a b. f (a -> b) -> f a -> f b

infixl apply as <*>
```

> [!tip]
> Apply often replaces the pattern of "building towards a final result"
> 
> Consider a function that [[Tuple|tuple]]s together its arguments
> ```haskell
> mk3Tuple a b c = a /\ b /\ c
> ```
> 
> A common situation is wanting to build something like this 3-tuple from some components that are trapped in a context like [[Maybe]] or [[Either]], and we want to say "when all these things are ok, build it"; this is exactly what Apply lets us do:
> 
> ```haskell
> maybeMk3Tuple :: Maybe a -> Maybe b -> Maybe c -> Maybe (a /\ b /\ c)
> maybeMk3Tuple ma mb mc = Just mk3Tuple <*> ma <*> mb <*> mc
>
> maybeMk3Tuple (Just 1) (Just 2) (Just 3)
> -- Just (1 /\ 2 /\ 3)
>
> maybeMk3Tuple (Just "a") (Just 3) (Nothing)
> -- Nothing
>
> maybeMk3Tuple Nothing Nothing Nothing
> -- Nothing
> ```

> [!tip]
> Obscure but occasionally usefully, Apply in collections lets us apply multiple functions to each element:
> ```haskell
> [(_ * 10), (_ * 20)] <*> [1, 2, 3]
> -- [10, 20, 20, 40, 30, 60]
> 
> [identity, const ", "] <*> ["a", "b", "c"]
> -- ["a", ",", "b", ",", "c", ","]
> ``` 

### Examples

lift `(a + b) / c` to [[Maybe]]
```haskell
f :: Number -> Number -> Number
f a b c = (a + b) / c

mf :: Maybe Number -> Maybe Number -> Maybe Number
mf ma mb mc = pure f <*> ma <*> mb <*> mc
```

Build up a `Person` [[Record|record]] from Maybe fields; short-circuiting to `Nothing` if any fields are `Nothing`
```haskell
type PartialPerson =
  { name :: Maybe String
  , email :: Maybe String
  , password :: Maybe String
  }

type Person =
  { name :: String
  , email :: String
  , password :: String
  }

person :: PartialPerson -> Person
person
  { name: name'
  , email: email'
  , password: password'
  } =
  let
    buildPerson name email password = {name, email, password}
  in
    Just buildPerson <*> name' <*> email' <*> password'
```