#lang racket

; Definitions introduce bindings into the dynamic environment, abbreviated env.
; Initially the dynamic environment is empty.
; env: = .

(define x 34)
; env: x --> 34, .

(define y 17)
; env: y --> 17, x --> 34, .
 
(define z (+ (+ x y) (+ y 2)))
; env: z --> 70, y --> 17, x --> 34, .
 
(define q (+ z 1))
; env: q --> 71, z --> 70, y --> 17, x --> 34, .

(define abs-of-z (if (< z 0) (- 0 z) z))
; env: abs-of-z --> 70, q --> 71, z --> 70, y --> 17, x --> 34, .