From 74d94fef72a140662e18a4682e84dc008eb2a260 Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop@gmail.com>
Date: Thu, 25 Jul 2024 20:02:00 -0400
Subject: [PATCH] Do not build ItemSet follow sets - #28

---
 lib/propane/parser.rb          | 46 ----------------------------------
 lib/propane/parser/item_set.rb |  4 ---
 2 files changed, 50 deletions(-)

diff --git a/lib/propane/parser.rb b/lib/propane/parser.rb
index 42b57b2..9882cbd 100644
--- a/lib/propane/parser.rb
+++ b/lib/propane/parser.rb
@@ -39,7 +39,6 @@ class Propane
       end
 
       build_reduce_actions!
-      build_follow_sets!
       build_tables!
       write_log!
       if @warnings.size > 0 && @options[:warnings_as_errors]
@@ -233,51 +232,6 @@ class Propane
       lookahead_tokens
     end
 
-    # Build the follow sets for each ItemSet.
-    #
-    # @return [void]
-    def build_follow_sets!
-      @item_sets.each do |item_set|
-        item_set.follow_set = build_follow_set_for_item_set(item_set)
-      end
-    end
-
-    # Build the follow set for the given ItemSet.
-    #
-    # @param item_set [ItemSet]
-    #   The ItemSet to build the follow set for.
-    #
-    # @return [Set]
-    #   Follow set for the given ItemSet.
-    def build_follow_set_for_item_set(item_set)
-      follow_set = Set.new
-      rule_sets_to_check_after = Set.new
-      item_set.items.each do |item|
-        (1..).each do |offset|
-          case symbol = item.next_symbol(offset)
-          when nil
-            rule_sets_to_check_after << item.rule.rule_set
-            break
-          when Token
-            follow_set << symbol
-            break
-          when RuleSet
-            follow_set += symbol.start_token_set
-            unless symbol.could_be_empty?
-              break
-            end
-          end
-        end
-      end
-      reduce_lookaheads = build_lookahead_reduce_actions_for_item_set(item_set)
-      reduce_lookaheads.each do |token, rule_set|
-        if rule_sets_to_check_after.include?(rule_set)
-          follow_set << token
-        end
-      end
-      follow_set
-    end
-
     def write_log!
       @log.puts Util.banner("Parser Rules")
       @grammar.rules.each do |rule|
diff --git a/lib/propane/parser/item_set.rb b/lib/propane/parser/item_set.rb
index 188436c..2fe8403 100644
--- a/lib/propane/parser/item_set.rb
+++ b/lib/propane/parser/item_set.rb
@@ -30,10 +30,6 @@ class Propane
       #   more than one rule that could be reduced.
       attr_accessor :reduce_actions
 
-      # @return [Set<Token>]
-      #   Follow set for the ItemSet.
-      attr_accessor :follow_set
-
       # Build an ItemSet.
       #
       # @param items [Array<Item>]