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


  [ dup 4 < iff [ 1 > ] done
    dup 1 & not iff [ drop false ] done
    true swap dup sqrt
    0 = iff [ 2drop not ] done
    1 >> times
      [ dup i^ 1 << 3 + mod 0 = if
          [ dip not conclude ] ]
    drop ]                              is isprime ( n --> b )
 