This is Polish notation [1], which puts a symbol for the function at the front of a term and the arguments of that function after it. So (* 2 3) is what you'd u

This is Polish notation [1], which puts a symbol for the function at the front of a term and the arguments of that function after it. So (* 2 3) is what you'd usually write as 2*3. So you can read this code: (define (expt n p) (if (equals? p 1) n (* n (expt n (- p 1))) As this more typical psuedocode function expt(n,p): if p = 1: return n return n * exp(n, p-1) Or the more mathematical framing: n^p = n * n^(p-1) [1] https://en.wikipedia.org/wiki/Polish_notation https://en.wikipedia.org/wiki/Polish_notation