Class: WeightedSelector

Inherits:
Object
  • Object
show all
Defined in:
lib/liquid/weighted_selector.rb

Instance Method Summary collapse

Constructor Details

#initialize ⇒ WeightedSelector

Returns a new instance of WeightedSelector.



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# File 'lib/liquid/weighted_selector.rb', line 5

def initialize
  @sums = []
  @elements = []
  @total = 0
end

Instance Method Details

#add(element, probability) ⇒ Object 



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# File 'lib/liquid/weighted_selector.rb', line 11

def add(element, probability)
  @elements << element
  @total += probability
  @sums << @total
end

#delete(element) ⇒ Object 



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# File 'lib/liquid/weighted_selector.rb', line 17

def delete(element)
  idx = @elements.index(element)
  if idx
    @total -= @sums[idx]
    @sums.delete_at(idx)
    @elements.delete_at(idx)
  end
end

#empty? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/liquid/weighted_selector.rb', line 30

def empty?
  @elements.empty?
end

#fill_up(element) ⇒ Object 



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# File 'lib/liquid/weighted_selector.rb', line 26

def fill_up(element)
  add(element, 1 - @total) if @total < 1
end

#pick ⇒ Object 



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# File 'lib/liquid/weighted_selector.rb', line 45

def pick
  pick_one
end

#pick_one ⇒ Object 



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# File 'lib/liquid/weighted_selector.rb', line 41

def pick_one
  pick_one_with_index[0] unless empty?
end

#pick_one_with_index ⇒ Object

stackoverflow.com/questions/4463561/weighed-random-selection-from-array



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# File 'lib/liquid/weighted_selector.rb', line 35

def pick_one_with_index
  rnd = Kernel.rand * @total
  idx = @sums.index { |x| x >= rnd }
  [@elements[idx], idx]
end