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Exercise_238.rkt

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+#lang racket
+
+(check-expect (inf-sup.v2 max (list 10 4 15 23 1 3 12 52 2)) 52)
+(check-expect (inf-sup.v2 min (list 10 4 15 23 1 3 12 52 2)) 1)
+
+(define (inf-sup.v2 f l)
+  (cond
+    [(empty? (rest l)) (first l)]
+    [else (f (first l) (inf-sup.v2 f (rest l)))]))
+
+; Determines the smallest number on l
+(check-expect (inf-2 (list 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1))
+              1)
+(check-expect (inf-2 (list 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25))
+              1)
+
+(define (inf-2 l)
+  (inf-sup.v2 min l))
+
+
+(check-expect (sup-2 (list 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1))
+              25)
+(check-expect (sup-2 (list 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25))
+              25)
+
+(define (sup-2 l)
+  (inf-sup.v2 max l))
+
+(check-expect (inf-sup > (list 5 4 3 23)) 23)
+(check-expect (inf-sup < (list 1 4 2)) 1)
+
+(define (inf-sup f l)
+  (cond
+    [(empty? (rest l)) (first l)]
+    [else
+     (if (f (first l)
+            (inf-sup f (rest l)))
+         (first l)
+         (inf-sup f (rest l)))]))
+
+(check-expect (inf-1 (list 5 1 2)) 1)
+
+(define (inf-1 l)
+  (inf-sup < l))
+
+(check-expect (sup-1 (list 4 1 6)) 6)
+
+(define (sup-1 l)
+  (inf-sup > l))

Exercise_239.rkt

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+#lang racket
+
+(cons 1 (cons 2 '()))
+
+(cons 23 (cons "a" '()))
+
+(cons "yellow" (cons #true '()))

Exercise_240.rkt

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+#lang racket
+
+(define-struct layer [stuff])
+
+(define LSTR0 "abcd")
+(define LSTR1 (make-layer "abcd"))
+(define LSTR2 (make-layer (make-layer (make-layer "abcd"))))
+
+(define LNUM0 4)
+(define LNUM1 (make-layer 10))
+(define LNUM2 (make-layer (make-layer (make-layer 2))))
+
+
+(define LITEM1 (make-layer "abcd"))
+(define LITEM2 (make-layer 10))

Exercise_241.rkt

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+#lang racket
+
+(define NELT1 (cons 20 '()))
+(define NELT2 (cons 5 (cons 10 '())))
+
+(define NELB1 (cons #true '()))
+(define NELB2 (cons #true (cons #false '())))
+
+
+(define NEL-T1 NELT1)
+(define NEL-T2 NELT2)
+
+
+(define NEL-B1 NELB1)
+(define NEL-B2 NELB2)

Exercise_242.rkt

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+#lang racket
+
+(check-expect (occurs "a" (list "b" "a" "d" "e")) (list "d" "e"))
+(check-expect (occurs "a" (list "b" "c" "d")) #f)
+
+(define (occurs s los)
+  los)

Exercise_243.rkt

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+#lang racket
+
+(define (f x) x)
+
+(cons f '())
+
+(f f)
+
+(cons f (cons 10 (cons (f 10) '())))

Exercise_244.rkt

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+#lang racket
+
+(define (f x) (x 10))
+
+(define (f x) (x f))
+
+(define (f x y) (x 'a y 'b))

Exercise_245.rkt

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+#lang racket
+
+(check-expect (function=at-1.2-3-and-5.775? x y) #false)
+(check-expect (function=at-1.2-3-and-5.775? x z) #false)
+
+(define (function=at-1.2-3-and-5.775? f1 f2)
+  (and (= (f1 1.2) (f2 1.2))
+       (= (f1 3) (f2 3))
+       (= (f1 -5.775) (f2 -5.775))))
+
+
+; Number -> Number
+(define (x n)
+  (+ n 2))
+
+; Number -> Number
+(define (y n)
+  (- n 3.5))
+
+; Number -> Number
+(define (z n)
+  (* n (/ 5 3)))