# Write a method that takes in an integer (greater than one) and
# returns true if it is prime; otherwise return false.
#
# You may want to use the `%` modulo operation. `5 % 2` returns the
# remainder when dividing 5 by 2; therefore, `5 % 2 == 1`. In the case
# of `6 % 2`, since 2 evenly divides 6 with no remainder, `6 % 2 == 0`.
# More generally, if `m` and `n` are integers, `m % n == 0` if and only
# if `n` divides `m` evenly.
#
# You would not be expected to already know about modulo for the
# challenge.
#
# Difficulty: medium.

def is_prime?(number)
  if number <= 1
    # only numbers > 1 can be prime.
    return false
  end

  idx = 2
  while idx < number
    if (number % idx) == 0
      return false
    end

    idx += 1
  end

  return true
end

# These are tests to check that your code is working. After writing
# your solution, they should all print true.

puts("\nTests for #is_prime?")
puts("===============================================")
    puts('is_prime?(2) == true: ' + (is_prime?(2) == true).to_s)
    puts('is_prime?(3) == true: ' + (is_prime?(3) == true).to_s)
    puts('is_prime?(4) == false: ' + (is_prime?(4) == false).to_s)
    puts('is_prime?(9) == false: ' + (is_prime?(9) == false).to_s)
puts("===============================================")