Module: MoreMath::RankingCommon

Included in:
Permutation, Subset
Defined in:
lib/more_math/ranking_common.rb

Overview

Common functionality for ranking systems. This module provides basic ranking operations that are shared across different ranking implementations in the MoreMath library, including permutations and subsets.

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#collection ⇒ Object? (readonly)

Returns the collection the #rank applies to if any was set, otherwise returns nil.

Returns:

  • (Object, nil) —

    the associated collection or nil



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# File 'lib/more_math/ranking_common.rb', line 26

def collection
  @collection
end

#last ⇒ Integer (readonly)

Returns the rank of the last ranked instance.

Returns:

  • (Integer) —

    the maximum rank value for this size



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# File 'lib/more_math/ranking_common.rb', line 20

def last
  @last
end

#rank ⇒ Integer (readonly)

Returns the rank of this instance, a Fixnum in the range of 0 and #last.

Returns:

  • (Integer) —

    the current rank



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# File 'lib/more_math/ranking_common.rb', line 15

def rank
  @rank
end

#size ⇒ Integer (readonly)

Returns the size of this instance’s collection, a Fixnum.

Returns:

  • (Integer) —

    the size of the collection



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# File 'lib/more_math/ranking_common.rb', line 9

def size
  @size
end

Instance Method Details

#each {|instance| ... } ⇒ self

Iterates over all instances starting with the first (rank == 0) ranked instance and ending with the last (rank == #last) ranked instance while yielding to a freshly created instance for every iteration step.

The mixed in methods from the Enumerable module rely on this method.

Yields:

  • (instance) —

    yields each instance in sequence

Returns:

  • (self) —

    returns self after iteration



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# File 'lib/more_math/ranking_common.rb', line 92

def each
  0.upto(last) do |r|
    klon = clone
    klon.rank = r
    yield klon
  end
  self
end

#each! {|instance| ... } ⇒ self

Does something similar to #each. It doesn’t create new instances (less overhead) for every iteration step, but yields to a modified self instead. This is useful if one only wants to call a method on the yielded value and work with the result of this call. It’s not a good idea to put the yielded values in a data structure because all of them will reference the same (this!) instance. If you want to do this use #each.

Yields:

  • (instance) —

    yields the current instance

Returns:

  • (self) —

    returns self after iteration



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# File 'lib/more_math/ranking_common.rb', line 110

def each!
  old_rank = rank
  0.upto(last) do |r|
    self.rank = r
    yield self
  end
  self
ensure
  self.rank = old_rank
end

#next ⇒ self Also known as: succ

Returns the next ranked instance. If this instance is the #last instance it returns the first (rank == 0) instance again.

Returns:

  • (self) —

    a new instance with incremented rank



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# File 'lib/more_math/ranking_common.rb', line 43

def next
  clone.next!
end

#next! ⇒ self Also known as: succ!

Switches this instance to the next ranked instance. If this was the #last instance it wraps around to the first (rank == 0) instance.

Returns:

  • (self) —

    returns self after incrementing rank



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# File 'lib/more_math/ranking_common.rb', line 32

def next!
  self.rank += 1
  self
end

#pred ⇒ self

Returns the previously ranked instance. If this was the first instance it returns the last (rank == #last) instance.

Returns:

  • (self) —

    a new instance with decremented rank



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# File 'lib/more_math/ranking_common.rb', line 62

def pred
  clone.pred!
end

#pred! ⇒ self

Switches this instance to the previously ranked instance. If this was the first instance it returns the last (rank == #last) instance.

Returns:

  • (self) —

    returns self after decrementing rank



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# File 'lib/more_math/ranking_common.rb', line 53

def pred!
  self.rank -= 1
  self
end

#random ⇒ self

Returns a randomly ranked instance.

Returns:

  • (self) —

    a new instance with random rank



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# File 'lib/more_math/ranking_common.rb', line 78

def random
  clone.random!
end

#random! ⇒ self

Switches this instance to a randomly ranked instance.

Returns:

  • (self) —

    returns self after setting random rank



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# File 'lib/more_math/ranking_common.rb', line 69

def random!
  new_rank = rand(last + 1).to_i
  self.rank = new_rank
  self
end