70 lines
1.3 KiB
Ruby
70 lines
1.3 KiB
Ruby
class Propane
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class Parser
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class Item
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attr_reader :rule
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attr_reader :position
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def initialize(rule, position)
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@rule = rule
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@position = position
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end
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def next_component
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@rule.components[@position]
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end
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def hash
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[@rule, @position].hash
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end
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def ==(other)
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@rule == other.rule && @position == other.position
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end
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def eql?(other)
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self == other
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end
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def closed_items
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if @rule.components[@position].is_a?(RuleSet)
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@rule.components[@position].rules.map do |rule|
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Item.new(rule, 0)
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end
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else
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[]
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end
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end
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def follow_symbol
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@rule.components[@position]
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end
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def followed_by?(symbol)
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follow_symbol == symbol
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end
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def next_position
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Item.new(@rule, @position + 1)
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end
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def to_s
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parts = []
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@rule.components.each_with_index do |symbol, index|
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if @position == index
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parts << "."
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end
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parts << symbol.name
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end
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if @position == @rule.components.size
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parts << "."
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end
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"#{@rule.name} -> #{parts.join(" ")}"
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end
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end
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end
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end
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