Task

Write a boolean function that tells whether a given integer is prime.



Remember that   1   and all non-positive numbers are not prime.

Use trial division.

Even numbers greater than   2   may be eliminated right away.

A loop from   3   to   √ n    will suffice,   but other loops are allowed.



Related tasks

   count in factors
   prime decomposition
   AKS test for primes
   factors of an integer
   Sieve of Eratosthenes
   factors of a Mersenne number
   trial factoring of a Mersenne number
   partition an integer X into N primes
   sequence of primes by Trial Division


(
  :n 3 :i n sqrt :m true :p
  (i m <=) (
    (n i mod 0 ==) (m @i false @p) when
    i 2 + @i
  ) while p
) :_prime?  ; helper function
 
(
  (
    ((2 <) (false))
    ((dup even?) (2 ==))
    ((true) (_prime?))
  ) case
) :prime?