Observe that our model of evaluation allows for combinations whose operators are compound expression. Use this observation to describe the behaviour of the following procedures:
(define (a-plus-abs-b a b)
(if (> b 0) + -) a b)if our argument b for the procedure a-plus-abs-b is bigger than 0, we will add a and b
$f(x) = a + b$
If our argument b for procedure a-plus-abs-b is less than 0, we will minus a and b
$f(x) = a - b$ where b is negative
Effectively, this means that a always adds to the absolute value of b
$f(x) = a + \lvert b \rvert$