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


define(`testnext',
   `ifelse(eval($2*$2>$1),1,
      1,
      `ifelse(eval($1%$2==0),1,
         0,
         `testnext($1,eval($2+2))')')')
define(`isprime',
   `ifelse($1,2,
      1,
      `ifelse(eval($1<=1 || $1%2==0),1,
         0,
         `testnext($1,3)')')')
 
isprime(9)
isprime(11)