random_stat_methods.rb

# A simulation for various dice rolling mechanisms
# For more information on how it was used. http://takeonrules.com/2015/09/10/running-a-fifth-edition-character-funnel/
#
# $ ruby random_stat_methods.rb
#
# I use `ruby random_stat_methods.rb | pbcopy` then paste that into a Google Spreadsheet to generate a chart.
class Simulation

  def initialize
    @scenarios = {}
  end

  def bonus_for(*values)
    ((values.inject(0) {|v,m| m += v} - 10) / 2).round
  end
  private :bonus_for

  def roll
    rand(6) + 1
  end
  private :roll

  def label_for(scenario:)
    @scenarios.fetch(scenario, scenario.to_s)
  end

  WORST_BONUS_POSSIBLE = -5 * 6

  def scenario_1
    @scenarios[__callee__] = "12 columns of 3d6 straight down"
    highest_bonus = WORST_BONUS_POSSIBLE
    (1..12).each do |iteration|
      current_bonus = 0
      (1..6).each do |stat|
        current_bonus += bonus_for(roll,roll,roll)
      end
      highest_bonus = current_bonus if current_bonus > highest_bonus
    end
    highest_bonus
  end

  def _scenario_2
    @scenarios[__callee__] = "4d6 straight down"
    current_bonus = 0
    (1..6).each do |stat|
      rolls = [roll,roll,roll, roll].sort.reverse[0..2]
      current_bonus += bonus_for(*rolls)
    end
    current_bonus
  end

  def scenario_3
    @scenarios[__callee__] = "4d6 straight down, optionally replace one with an 8"
    bonuses = []
    (1..6).each do |stat|
      rolls = [roll,roll,roll, roll].sort.reverse[0..2]
      bonuses << bonus_for(*rolls)
    end
    bonuses << -1
    bonuses.sort.reverse[0..5].inject(0) { |v,m| m += v }
  end

  def _scenario_4
    @scenarios[__callee__] = "4d6 straight down, optionally replace one with a 10"
    bonuses = []
    (1..6).each do |stat|
      rolls = [roll,roll,roll, roll].sort.reverse[0..2]
      bonuses << bonus_for(*rolls)
    end
    bonuses << 0
    bonuses.sort.reverse[0..5].inject(0) { |v,m| m += v }
  end

  def _scenario_5
    @scenarios[__callee__] = "4d6 straight down, optionally replace one with a 7"
    bonuses = []
    (1..6).each do |stat|
      rolls = [roll,roll,roll, roll].sort.reverse[0..2]
      bonuses << bonus_for(*rolls)
    end
    bonuses << -2
    bonuses.sort.reverse[0..5].inject(0) { |v,m| m += v }
  end
end

SIMULATIONS = (ENV['SIMULATIONS'] || 10_000).to_i
results = {}
simulation = Simulation.new
scenarios = simulation.methods.grep(/^scenario/)

scenarios.each_with_object(results) do |scenario_name, object|
  object[scenario_name] = {}
  (1..SIMULATIONS).each do |i|
    bonus = simulation.public_send(scenario_name)
    object[scenario_name][bonus] ||= 0
    object[scenario_name][bonus] += 1
  end
  object
end

min = 24
max = -24
results.values.each do |value|
  sorted = value.keys.sort
  max = sorted[-1] if sorted[-1] > max
  min = sorted[0] if sorted[0] < min
end

print "Modifier\t"
print scenarios.map { |scenario| simulation.label_for(scenario: scenario) }.join("\t")
print "\n"
(min..max).each do |i|
  print "#{i}"
  scenarios.each do |scenario_name|
    print "\t#{results[scenario_name][i] || 0}"
  end
  print "\n"
end