Problem 4 on Project Euler

p4.rb

class Numeric
  def palindromic?
    to_s.reverse == to_s
  end
end

class Range
  def reverse
    ReverseRange.new last, first, exclude_end?
  end
end

class ReverseRange < Range
  def each &blk
    cur = first
    blk[cur] until (cur = cur.pred) == last
  end
end

largest = (100..999).reverse.collect do |i|
  possible = (100..i).reverse.find do |j|
    product = i * j
    product.palindromic?
  end || 0
  i * possible
end.max
puts largest