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Contents
require 'arc-furnace/source'
# An unfold is the reverse of a fold--it takes a single value an blows it out
# into an enumeration of values. Useful for splitting up rows into multiple output
# rows and whatnot. Only #unfold is required for implementation.
module ArcFurnace
class Unfold < Source
private_attr_reader :source, :unfolded
def initialize(source:)
@source = source
@value = nil
end
def value
if @value.nil? && !empty?
advance
end
@value
end
# Given a row from the source, produce the unfolded rows as a result. This method must return
# an array.
def unfold(row)
raise "Unimplemented!"
end
def empty?
@value.nil? && source.empty?
end
def advance
while (unfolded.nil? || unfolded.empty?) && !source.empty?
# Use reverse since we want to process in-order, but, #pop is much faster than #unshift
@unfolded = unfold(source.row.deep_dup)
unfolded.reverse!
end
if unfolded && !unfolded.empty?
@value = unfolded.pop
else
@value = nil
end
end
end
end
Version data entries
38 entries across 38 versions & 1 rubygems