lenses.hs

traverseX :: forall f. Functor f = (a -> f a) -> Vec3 a -> f (Vec3 a)
traverseX f (Vec3 x y z) = (\h -> Vec3 h) <$> f x

traverseY :: forall f. Functor f = (a -> f a) -> Vec3 a -> f (Vec3 a)
traverseY f (Vec3 x y z) = (\h -> Vec3 h) <$> f x

traverseZ :: forall f. Functor f = (a -> f a) -> Vec3 a -> f (Vec3 a)
traverseZ f (Vec3 x y z) = (\h -> Vec3 h) <$> f x

type Lens s a = forall f. Funtor f => (a -> f a) -> s -> f s

_X :: Lens a (Vec3 a)
_X = traverseX

_Y :: Lens a (Vec3 a)
_Y = traverseY

_Z :: Lens a (Vec3 a)
_Z = traverseZ


-- > over _X (+1) (Vec3 1 0 7)

-- this is just for visual prettification, its just "flipped application"
(&) = flip ($)

(%~) = over

-- We can use it like this
-- > (Vec3 1 0 7) & _X %~ (+1)