const incr = x => x + 1
const add  = curry((x, y) => x + y)
const sum3 = curry((x, y, z) => x + y + z)

liftA(incr, Functor1) === pure(incr).ap(Functor1)
liftA2(add, Functor1, Functor2) === pure(add).ap(Functor1).ap(Functor2)
liftA3(sum3, Functor1, Functor2, Functor3) === pure(sum3).ap(Functor1).ap(Functor2).ap(Functor3)