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Abundant, deficient and perfect number classifications: Difference between revisions

Abundant, deficient and perfect number classifications (view source)

Revision as of 21:08, 9 March 2015

203 bytes removed ,  9 years ago
→‎{{header|Racket}}: Much shorter code
(Added Bracmat solution)
(→‎{{header|Racket}}: Much shorter code)
Line 568:
 
=={{header|Racket}}==
 
We use use '''fold-divisors''' from [[Proper_divisors#Racket]].
 
 
<lang racket>#lang racket
(require "proper-divisors.rkt"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)))))
 
▲(definelet SCOPE([N 20000])
(define P
(letdefine t ((Pmake-v (vector)hasheq))
(for ([i (λin-range 1 (nadd1 N))])
(set!define P-vc (fold-divisors P-v n 0classify +i))
(hash-set! t c (vectoradd1 (hash-ref P-vt c n0))))
(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>
BetweenThe range between 1 and 20000 has:
4953 abundant numbers
15043 deficient numbers
4 perfect numbers
▲ ~a4953 abundant numbers
</pre>
 
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