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


' Test and display primes 1 .. 50
for i = 1 TO 50
  if prime(i) <> 0 then print i;" ";
next i
 
FUNCTION prime(n)
if n < 2         then prime = 0 : goto [exit]
if n = 2         then prime = 1 : goto [exit]
if n mod 2 = 0   then prime = 0 : goto [exit]
prime = 1
for i = 3 to int(n^.5) step 2
 if n mod i = 0 then  prime = 0 : goto [exit]
next i
[exit]
END FUNCTION