Rename to propane

lib/propane/parser/item.rb

@@ -0,0 +1,69 @@
+class Propane
+  class Parser
+
+    class Item
+
+      attr_reader :pattern
+      attr_reader :position
+
+      def initialize(pattern, position)
+        @pattern = pattern
+        @position = position
+      end
+
+      def next_component
+        @pattern.components[@position]
+      end
+
+      def hash
+        [@pattern, @position].hash
+      end
+
+      def ==(other)
+        @pattern == other.pattern && @position == other.position
+      end
+
+      def eql?(other)
+        self == other
+      end
+
+      def closed_items
+        if @pattern.components[@position].is_a?(Rule)
+          @pattern.components[@position].patterns.map do |pattern|
+            Item.new(pattern, 0)
+          end
+        else
+          []
+        end
+      end
+
+      def follow_symbol
+        @pattern.components[@position]
+      end
+
+      def followed_by?(symbol)
+        follow_symbol == symbol
+      end
+
+      def next_position
+        Item.new(@pattern, @position + 1)
+      end
+
+      def to_s
+        parts = []
+        @pattern.components.each_with_index do |symbol, index|
+          if @position == index
+            parts << "."
+          end
+          parts << symbol.name
+        end
+        if @position == @pattern.components.size
+          parts << "."
+        end
+        "#{@pattern.rule.name} -> #{parts.join(" ")}"
+      end
+
+    end
+
+  end
+end

lib/propane/parser/item_set.rb

@@ -0,0 +1,76 @@
+class Propane
+  class Parser
+
+    class ItemSet
+
+      attr_reader :items
+
+      attr_accessor :id
+
+      # @return [Hash]
+      #   Maps a follow symbol to its item set.
+      attr_reader :follow_item_set
+
+      # @return [Set]
+      #   Item sets leading to this item set.
+      attr_reader :in_sets
+
+      def initialize(items)
+        @items = Set.new(items)
+        @follow_item_set = {}
+        @in_sets = Set.new
+        close!
+      end
+
+      def follow_symbols
+        Set.new(@items.map(&:follow_symbol).compact)
+      end
+
+      def build_follow_set(symbol)
+        ItemSet.new(items_followed_by(symbol).map(&:next_position))
+      end
+
+      def hash
+        @items.hash
+      end
+
+      def ==(other)
+        @items.eql?(other.items)
+      end
+
+      def eql?(other)
+        self == other
+      end
+
+      def to_s
+        @items.map(&:to_s).join("\n")
+      end
+
+      private
+
+      def close!
+        eval_items = @items
+        while eval_items.size > 0
+          this_eval_items = eval_items
+          eval_items = Set.new
+          this_eval_items.each do |item|
+            item.closed_items.each do |new_item|
+              unless @items.include?(new_item)
+                eval_items << new_item
+              end
+            end
+          end
+          @items += eval_items
+        end
+      end
+
+      def items_followed_by(symbol)
+        @items.select do |item|
+          item.followed_by?(symbol)
+        end
+      end
+
+    end
+
+  end
+end