[Ruby] exercise _ Prime

Write a method prime? that takes in a number and returns a boolean, indicating whether the number is prime. A prime number is only divisible by 1 and itself.

 

def prime?(num)

end

puts prime?(2)  #=> true
puts prime?(5)  #=> true
puts prime?(11) #=> true
puts prime?(4)  #=> false
puts prime?(9)  #=> false
puts prime?(-5) #=> false

def prime?(num)
  if num < 2
    return false
  end

  (2...num).each do |factor|
    if num % factor == 0
      return false
    end
  end

  return true
end

puts prime?(2)  #=> true
puts prime?(5)  #=> true
puts prime?(11) #=> true
puts prime?(4)  #=> false
puts prime?(9)  #=> false
puts prime?(-5) #=> false