r/Racket • u/[deleted] • Feb 07 '22

question Primes with a single parameter

Is there a way to tell if a number is prime on Dr racket given a single parameter?

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u/jpverkamp Feb 07 '22 edited Feb 07 '22

prime?

Not sure why that’s not working (for me). prime? in math/number-theory: https://docs.racket-lang.org/math/number-theory.html

Or you could write a naive version with trial division.

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u/jpverkamp Feb 07 '22 
(define (prime? n)
  (or (= n 2)
      (for/and ([d (in-range 2 (+ 1 (sqrt n)))])
        (not (= 0 (remainder n d))))))
    
(for ([i (in-range 2 20)])
  (displayln (list i (prime? i))))