Quick dice roller script.

dice.rb

class Array
  def sum
    reduce(0) { |sum, x| sum + x }
  end
end

class Dice
  def self.roll(sides = 6)
    rand(sides) + 1
  end
end

class RollResults
  def initialize(rolls = [], opts = {})
    @rolls = rolls
    @opts = opts
  end
  attr_reader :rolls, :opts

  def self.roll(num = 1, opts = {:sides => 6})
    rolls = num.times.collect { Dice.roll(opts[:sides]) }
    new(rolls, opts)
  end

  def describe
    msg = if rolls.length > 1 || opts[:change]
      "[#{rolls.join(',')}]" << " Sum: #{rolls.sum + (opts[:change] || 0)}"
    else
      rolls.first.to_s
    end
  end
end

class WoDRoller < RollResults
  def self.roll(num = 1, opts = {})
    opts = default_options.merge! opts
    if num == :chance
      opts[:chance] = true
      num = 1
    end

    rolls = [num.times.collect { Dice.roll(10) }]
    return new(rolls, opts) if opts[:chance]

    until (exploders = rolls.last.select { |num| num >= opts[:explosion_threshold] }).empty?
      rolls << exploders.collect { Dice.roll(10) }
    end
    return new(rolls, opts)
  end

  def self.default_options
    { :chance => false,
      :success_threshold => 8,
      :explosion_threshold => 10 }
  end

  def describe
    if opts[:chance]
      chance_die = rolls.flatten.first
      (chance_die == 10 ? 'Success' : 'Failure') << " [#{chance_die}]"
    else
      successes = rolls.flatten.select { |num| num >= opts[:success_threshold] }
      success = successes.empty?.!

      if success
        exceptional = successes.length >= 5
        [ (exceptional ? 'Exceptional ' : '') << 'Success',
          rolls.collect { |roll| "[#{roll.join(',')}]" }.join(' '),
          "with #{successes.length} successes"
        ].join(' ')
      else
        "Failure [#{rolls.first.join(',')}]"
      end
    end
  end
end

class ORERoller < RollResults
  def self.roll(num = 1, opts = {})
    rolls = [num.times.collect { Dice.roll(10) }]
    new(rolls, opts)
  end

  def describe
    sets = rolls.first.group_by { |x| x }.sort.collect do |height, set|
      next if set.length == 1
      "#{set.length}x#{height}"
    end.compact.<<("[#{rolls.first.sort.join(',')}]").join(' ')
  end
end