number palindrome

# Return a boolean indicating whether the number is a palindrome. Raises a
# TypeError if the argument is not an integer
#
# Caveat: Try to accomplish this without converting the number to a string.
#   The goal is to understand your approach to a problem with constraints
#   rather than seeing how quickly you can jump to an easy solution.
#
# Example
#   palindrome?(1001) => true
#   palindrome?(1234) => false
#   palindrome?(1)    => true, `1` backwards is `1`
#   palindrome?(10)   => false, read backward, the number is effectively `1`
#   palindrome?(-121) => false, the `-` sign is included

module Positional
  refine Integer do
    def position_rtl(index)
      self / (10**index) % 10
    end
  end
end

class Exercise
  using Positional
  
  attr_reader :number
  
  def initialize(number)
    @number = number
    
    raise TypeError unless number.kind_of?(Integer)
  end

  def palindrome?
    return false if number < 0
    
    size = Math.log(number, 10).floor + 1
    size.times do |i|
      return false unless number.position_rtl(size - 1 - i) ==  number.position_rtl(i)
    end
    
    true
  end
end

Exercise.new(1001).palindrome?
Exercise.new(1234).palindrome?
Exercise.new(1).palindrome?
Exercise.new(10).palindrome?
Exercise.new(-121).palindrome?