add dir

.gitignore

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+*.jpg
+*.pdf

hw4/hw4.rkt

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+
+#lang racket
+
+(provide (all-defined-out)) ;; so we can put tests in a second file
+
+;; put your code below
+(define (sequence low high stride) 
+	(if (> low high)
+		null
+		(cons low (sequence (+ low stride) high stride))))
+
+(define (string-append-map xs suffix) 
+	(map (lambda (s) (string-append s suffix)) xs))
+
+(define (list-nth-mod xs n)
+	(if (< n 0)
+		(error "list-nth-mod: negative number")
+		(if (null? xs)
+			(error "list-nth-mod: empty list")
+			(car (list-tail xs (remainder n (length xs)))))))
+
+(define (stream-for-n-steps s n)
+	(if (> n 0)
+		(cons (car (s)) (stream-for-n-steps (cdr (s)) (- n 1)))
+		null))
+
+(define funny-number-stream 
+	(letrec ([f 
+		(lambda (x) (cons 
+			(if (= 0 (remainder x 5)) (- 0 x) x) 
+			(lambda () (f (+ x 1)))))])
+	(lambda () (f 1))))
+
+(define dan-then-dog 
+	(lambda () (cons "dan.jpg" (lambda () (cons "dog.jpg" dan-then-dog)))))
+
+(define (stream-add-zero s) 
+	(lambda () (cons (cons 0 (car (s))) 
+					(stream-add-zero (cdr (s))))))
+
+(define (cycle-lists xs ys) 
+	(define (f n) 
+		(lambda () (cons 
+			(cons (list-nth-mod xs n) (list-nth-mod ys n))
+			(f (+ 1 n)))))
+	(f 0))
+
+(define (vector-assoc v vec)
+	(letrec ([l (vector-length vec)]
+		[f (lambda (n) 
+			(if (= l n) #f
+				(let ([ref (vector-ref vec n)])
+					(if (pair? ref) 
+						(if (equal? v (car ref)) ref (f (+ 1 n)))
+						(f (+ 1 n))))))])
+	(f 0)))
+
+(define (cached-assoc xs n)
+	(let ([cache (make-vector n #f)]
+		[pos 0])
+	(lambda (v)
+		(let ([cr (vector-assoc v cache)])
+			(if cr cr
+			(let ([xr (assoc v xs)])
+				(if xr 
+					(begin (vector-set! cache pos xr)
+						(set! pos (if (= (+ 1 pos) n) 0 (+ 1 pos)))
+						xr)
+					#f)))))))
+
+(define-syntax while-less
+	(syntax-rules (do)
+		[(while-less e1 do e2) 
+		(letrec ([x e1]
+			[thunk (lambda () (cons e2 thunk))]
+			[f (lambda (t) 
+				(if (< (car (t)) x)
+					(f (cdr (t)))
+					#t))])
+		(f thunk))]))

hw4/hw4test.rkt

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+#lang racket
+;; Programming Languages Homework4 Simple Test
+;; Save this file to the same directory as your homework file
+;; These are basic tests. Passing these tests does not guarantee that your code will pass the actual homework grader
+
+;; Be sure to put your homework file in the same folder as this test file.
+;; Uncomment the line below and change HOMEWORK_FILE to the name of your homework file.
+(require "hw4.rkt")
+(require rackunit)
+
+;; Helper functions
+(define ones (lambda () (cons 1 ones)))
+(define a 2)
+
+(define tests
+  (test-suite
+   "Sample tests for Assignment 4"
+
+   ; sequence test
+   (check-equal? (sequence 0 5 1) (list 0 1 2 3 4 5) "Sequence test")
+
+   ; string-append-map test
+   (check-equal? (string-append-map 
+                  (list "dan" "dog" "curry" "dog2") 
+                  ".jpg") '("dan.jpg" "dog.jpg" "curry.jpg" "dog2.jpg") "string-append-map test")
+
+   ; list-nth-mod test
+   (check-equal? (list-nth-mod (list 0 1 2 3 4) 2) 2 "list-nth-mod test")
+
+   ; stream-for-n-steps test
+   (check-equal? (stream-for-n-steps (lambda () (cons 1 ones)) 1) (list 1) "stream-for-n-steps test")
+
+   ; funny-number-stream test
+   (check-equal? (stream-for-n-steps funny-number-stream 16) (list 1 2 3 4 -5 6 7 8 9 -10 11 12 13 14 -15 16) "funny-number-stream test")
+
+   ; dan-then-dog test
+   (check-equal? (stream-for-n-steps dan-then-dog 1) (list "dan.jpg") "dan-then-dog test")
+
+   ; stream-add-zero test
+   (check-equal? (stream-for-n-steps (stream-add-zero ones) 1) (list (cons 0 1)) "stream-add-zero test")
+
+   ; cycle-lists test
+   (check-equal? (stream-for-n-steps (cycle-lists (list 1 2 3) (list "a" "b")) 3) (list (cons 1 "a") (cons 2 "b") (cons 3 "a")) 
+                 "cycle-lists test")
+
+   ; vector-assoc test
+   (check-equal? (vector-assoc 4 (vector (cons 2 1) (cons 3 1) (cons 4 1) (cons 5 1))) (cons 4 1) "vector-assoc test")
+
+   ; cached-assoc tests
+   (check-equal? ((cached-assoc (list (cons 1 2) (cons 3 4)) 3) 3) (cons 3 4) "cached-assoc test")
+
+   ; while-less test
+   (check-equal? (while-less 7 do (begin (set! a (+ a 1)) a)) #t "while-less test")
+
+   ))
+
+(require rackunit/text-ui)
+;; runs the test
+(run-tests tests)