Sum and length

Write a recursive function sum_and_length that simultaneously computes the sum and the length of an array, returning a list with two elements: the first element is the sum, and the second element is the length.

Let the sum of an empty array be 0. Do not use the sum or len functions or loops.

Example behavior

>>> sum_and_length([])
[0, 0]
>>> sum_and_length([1,2,3])
[6, 3]
>>> sum_and_length([1,2,3,4,5,6,7,8,9,10])
[55, 10]