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('isprime(n)i,max') :(isprime_end)
isprime isprime = n
        le(n,1) :s(freturn)
        eq(n,2) :s(return)
        eq(remdr(n,2),0) :s(freturn)
        max = sqrt(n); i = 1
isp1    i = le(i + 2,max) i + 2 :f(return)
        eq(remdr(n,i),0) :s(freturn)f(isp1)
isprime_end