Method: IntervalNotation::SweepLine.segmentation_by_boundary_points

Defined in:
lib/interval_notation/sweep_line/sweep_line.rb

.segmentation_by_boundary_points(boundary_points, initial_state) ⇒ Object

Make a segmentation using sweep line along boundary points.



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# File 'lib/interval_notation/sweep_line/sweep_line.rb', line 61

def self.segmentation_by_boundary_points(boundary_points, initial_state)
  if boundary_points.empty?
    segment = Segmentation::Segment.new(BasicIntervals::OpenOpenInterval.new(-Float::INFINITY, Float::INFINITY), initial_state)
    return Segmentation.new([segment])
  end

  point_chunks = boundary_points.sort_by(&:value).chunk(&:value).to_a
  state = initial_state

  # Process minus-infinity points which can change initial state
  if point_chunks.first.first == -Float::INFINITY
    point_value, points_at_minus_infinity = point_chunks.shift
    state = state.state_after_point(points_at_minus_infinity)
  end

  # Remove plus-infinity points as they can change state but this won't be reflected by any interval
  if point_chunks.last.first == Float::INFINITY
    point_value, points_at_plus_infinity = point_chunks.pop
  end

  prev_point_value = -Float::INFINITY
  segments = []
  # We removed points at plus or minus infinity so now we process inner points
  point_chunks.each do |point_value, points_on_place|
    segments << Segmentation::Segment.new(BasicIntervals::OpenOpenInterval.new(prev_point_value, point_value), state)
    segments << Segmentation::Segment.new(BasicIntervals::Point.new(point_value), state.state_at_point(points_on_place))
    state = state.state_after_point(points_on_place)
    prev_point_value = point_value
  end

  # add fictive segment up to plus-infinity point (may be fictive)
  segments << Segmentation::Segment.new(BasicIntervals::OpenOpenInterval.new(prev_point_value, Float::INFINITY), state)
  Segmentation.new(segments, skip_validation: true) # here we can skip validation but not normalization
end