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


is_prime = (n) ->
  # simple prime detection using trial division, works
  # for all integers
  return false if n <= 1 # by definition
  p = 2
  while p * p <= n
    return false if n % p == 0
    p += 1
  true
 
for i in [-1..100]
  console.log i if is_prime i