#### Reading material

Pages 59-62.
#### Additional material

The LISP function
(DEFUN product (n) (IF (zerop n) 0 (+ (product (1- n)) m)))

can be expressed in Standard ML as
fun product(n) = if n = 0 then 0 else product(n-1) + m

or
fun product(0) = 0
| product(n) = product(n-1) + m

**Question**

Consider the following function in Standard ML.

fun t(0) = 1
| t(n) = t(n - 1) + t(n - 1)

What does this function compute? How can we use the induction tool
to prove the above function correct.