303.rkt

;; The first three lines of this file were inserted by DrRacket. They record metadata
;; about the language level of this file in a form that our tools can easily process.
#reader(lib "htdp-intermediate-lambda-reader.ss" "lang")((modname 303ex) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f () #f)))
;; Exercise 303
;; ------------
;; Draw arrows from the shaded occurrences of x to their binding occurrences in
;; each of the following three lambda expressions:
;;
;;    (lambda (x y)
;;      (+ x (* x y)))
;;    
;;    (lambda (x y)
;;      (+ x
;;         (local ((define x (* y y)))
;;           (+ (* 3 x)
;;              (/ 1 x))))) 
;;    
;;    (lambda (x y)
;;      (+ x
;;         ((lambda (x)
;;            (+ (* 3 x)
;;               (/ 1 x)))
;;          (* y y))))
;;
;; Also draw a box for the scope of each shaded x and holes in the scope as
;; necessary. 
;; -----------------------------------------------------------------------------

(require 2htdp/image)
(bitmap "ex-303.png")

(lambda (x y)
  (+ x (* x y)))

(lambda (x y)
  (+ x
     (local ((define x (* y y)))
       (+ (* 3 x)
          (/ 1 x))))) 

(lambda (x y)
  (+ x
     ((lambda (x)
        (+ (* 3 x)
           (/ 1 x)))
      (* y y))))