Add assignment 1 and gitignore for unwanted files.

.gitignore

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+*.bak

assignments/A1/assignment-1.rkt

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+(module assignment1 racket
+  ;question 1
+  (define (drop-divisible divisor number-list)
+    (filter (lambda (x)
+              (or
+               (not
+                (eq? (modulo x divisor) 0))
+               (eq? x divisor)))
+            number-list))
+
+  ;question 2
+  (define (sieve-with divisor-list number-list)
+    (define (iter divs lst)
+      (cond
+        [(empty? divs) lst]
+        [else (iter (rest divs) (drop-divisible (first divs) lst))]))
+    (iter divisor-list number-list))
+
+  ;question 3
+  (define (sieve potential-prime)
+    ;never need to check for primes below 2
+    ;you also never need to check for a number above the square root in a given range
+    ;plus one just for off by one errors
+    (sieve-with (range 2 (+ (integer-sqrt potential-prime) 1)) (range 2 potential-prime)))
+    
+
+  (module+ test
+    (require rackunit)
+    (check-equal? (drop-divisible 2 (list 2 3 4 5 6 7 8 9 10)) (list 2 3 5 7 9))
+    (check-equal? (drop-divisible 3 (list 2 3 4 5 6 7 8 9 10)) (list 2 3 4 5 7 8 10))
+    (check-equal? (drop-divisible 5 (list 2 3 4 5 6 7 8 9 10)) (list 2 3 4 5 6 7 8 9))
+
+    (check-equal? (sieve-with '(2 3) (list 2 3 4 5 6 7 8 9 10)) (list 2 3 5 7))
+    (check-equal? (sieve-with '() (list 2 3 4 5 6 7 8 9 10)) (list 2 3 4 5 6 7 8 9 10))
+
+    (check-equal? (sieve 10) (list 2 3 5 7))
+
+    ;question 4
+    (require math/number-theory)
+    (check-equal? (sieve 100) (filter prime? (range 1 100)))
+    (check-equal? (sieve 100000) (filter prime? (range 1 100000)))
+    ))