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


data primes;
do n=1 to 1000;
  link primep;
  if primep then output;
end;
stop;
 
primep:
if n < 4 then do;
  primep=n=2 or n=3;
  return;
end;
primep=0;
if mod(n,2)=0 then return;
do k=3 to sqrt(n) by 2;
  if mod(n,k)=0 then return;
end;
primep=1;
return;
keep n;
run;