Abundant, deficient and perfect number classifications: Difference between revisions

Content added Content deleted

Inline

@@ Line 568: / Line 568: @@
 =={{header|Racket}}==
-We use use '''fold-divisors''' from [[Proper_divisors#Racket]].
 <lang racket>#lang racket
-(require "proper-divisors.rkt")
+(require math)
+(define (proper-divisors n) (drop-right (divisors n) 1))
-(define SCOPE 20000)
+(define classes '(deficient perfect abundant))
+(define (classify n)
+  (list-ref classes (add1 (sgn (- (apply + (proper-divisors n)) n)))))
+(let ([N 20000])
-(define P
-  (let ((P-v (vector)))
+  (define t (make-hasheq))
-    (λ (n)
+  (for ([i (in-range 1 (add1 N))])
-      (set! P-v (fold-divisors P-v n 0 +))
+    (define c (classify i))
-      (vector-ref P-v n))))
+    (hash-set! t c (add1 (hash-ref t c 0))))
+  (printf "The range between 1 and ~a has:\n" N)
+  (for ([c classes]) (printf "  ~a ~a numbers\n" (hash-ref t c 0) c)))</lang>
-(define-values
-  (a d p)
-  (for/fold ((a 0) (d 0) (p 0))
-            ((n (in-range SCOPE 0 -1))) ; doing this backwards initialises the memo
-    (match (- (P n) n)
-      [0             (values a d (add1 p))]    ; perfect
-      [(? negative?) (values a (add1 d) p)]    ; deficient
-      [(? positive?) (values (add1 a) d p)]))) ; abundant
-(printf #<<EOS
-Between 1 and ~s:
-  ~a abundant numbers
-  ~a deficient numbers
-  ~a perfect numbers
-EOS
-        SCOPE a d p)</lang>
 {{out}}
 <pre>
-Between 1 and 20000:
+The range between 1 and 20000 has:
-abundant numbers
 deficient numbers
 perfect numbers
+abundant numbers
 </pre>