1 files changed, 38 insertions, 0 deletions
diff --git a/tool/lrama/lib/lrama/state/reduce.rb b/tool/lrama/lib/lrama/state/reduce.rb
new file mode 100644
index 0000000000..a2b7c26cfe
--- /dev/null
+++ b/tool/lrama/lib/lrama/state/reduce.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+module Lrama
+  class State
+    class Reduce
+      # https://www.gnu.org/software/bison/manual/html_node/Default-Reductions.html
+      attr_reader :item, :look_ahead, :not_selected_symbols
+      attr_accessor :default_reduction
+
+      def initialize(item)
+        @item = item
+        @look_ahead = nil
+        @not_selected_symbols = []
+      end
+
+      def rule
+        @item.rule
+      end
+
+      def look_ahead=(look_ahead)
+        @look_ahead = look_ahead.freeze
+      end
+
+      def add_not_selected_symbol(sym)
+        @not_selected_symbols << sym
+      end
+
+      def selected_look_ahead
+        if @look_ahead
+          # @type ivar @look_ahead: Array<Grammar::Symbol>
+          @look_ahead - @not_selected_symbols
+        else
+          []
+        end
+      end
+    end
+  end
+end