class MoreMath::Subset

Returns the subset of the collection +collection+ for the rank +rank+.

def self.for(collection, rank = 0)
  subset = new(collection.size, rank)
  subset.instance_variable_set(:@collection, collection)
  subset
end

Returns the power set of the collection +collection+.

def self.power_set(collection)
  self.for(collection).map(&:value)
end

+rank+.
Returns a Subset instance for a collection of size +size+ with the rank

def initialize(size, rank = 0)
  @size, self.rank = size, rank
  @last = (1 << size) - 1
end

Assigns m to the rank attribute of this object.

def rank=(m)
  @rank = m % (1 << size)
end

set it applies to the array [ 0, 1, ..., size - 1 ] instead.)
Returns the subset for rank #rank and #collection. (If no collection was

def value
  result = []
  c = @collection || (0...size).to_a
  r = @rank
  0.upto(size) do |i|
    r[i] == 1 and result << c[i]
  end
  result
end

Modules