From 9cc1890ddc378b4241b5f99e7391ea7b42210324 Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop@gmail.com>
Date: Sat, 28 Aug 2021 10:28:50 -0400
Subject: [PATCH] One Rule object stores all alternative patterns

---
 lib/imbecile.rb             | 37 +++++++++++++++++++------------------
 lib/imbecile/parser.rb      |  5 ++---
 lib/imbecile/parser/item.rb | 18 +++++++++---------
 lib/imbecile/rule.rb        | 26 ++++++++++++++++++++------
 4 files changed, 50 insertions(+), 36 deletions(-)

diff --git a/lib/imbecile.rb b/lib/imbecile.rb
index 85fb185..fb810f6 100644
--- a/lib/imbecile.rb
+++ b/lib/imbecile.rb
@@ -36,7 +36,7 @@ class Imbecile
 
   def initialize(input)
     @tokens = []
-    @rules = []
+    @rules = {}
     input = input.gsub("\r\n", "\n")
     while !input.empty?
       parse_grammar(input)
@@ -79,9 +79,10 @@ class Imbecile
       pattern = $1
       @tokens << Token.new(nil, pattern, @tokens.size)
     elsif input.slice!(/\A(\S+)\s*:\s*\[(.*?)\] <<\n(.*?)^>>\n/m)
-      rule_name, rule, code = $1, $2, $3
-      rule = rule.strip.split(/\s+/)
-      @rules << Rule.new(rule_name, rule, code)
+      rule_name, components, code = $1, $2, $3
+      components = components.strip.split(/\s+/)
+      @rules[rule_name] ||= Rule.new(rule_name)
+      @rules[rule_name].add_pattern(components, code)
     else
       if input.size > 25
         input = input.slice(0..20) + "..."
@@ -97,24 +98,24 @@ class Imbecile
       end
       token_names[token.name] = token
     end
-    rule_names = @rules.each_with_object({}) do |rule, rule_names|
-      if token_names.include?(rule.name)
-        raise Error.new("Rule name collides with token name #{rule.name}")
+    @rules.each do |rule_name, rule|
+      if token_names.include?(rule_name)
+        raise Error.new("Rule name collides with token name #{rule_name}")
       end
-      rule_names[rule.name] ||= []
-      rule_names[rule.name] << rule
     end
-    unless rule_names["Start"]
+    unless @rules["Start"]
       raise Error.new("Start rule not found")
     end
-    @rules.each do |rule|
-      rule.components.map! do |component|
-        if token_names[component]
-          token_names[component]
-        elsif rule_names[component]
-          rule_names[component]
-        else
-          raise Error.new("Symbol #{component} not found")
+    @rules.each do |rule_name, rule|
+      rule.patterns.each do |pattern|
+        pattern.components.map! do |component|
+          if token_names[component]
+            token_names[component]
+          elsif @rules[component]
+            @rules[component]
+          else
+            raise Error.new("Symbol #{component} not found")
+          end
         end
       end
     end
diff --git a/lib/imbecile/parser.rb b/lib/imbecile/parser.rb
index 8a1c923..97789a2 100644
--- a/lib/imbecile/parser.rb
+++ b/lib/imbecile/parser.rb
@@ -3,9 +3,8 @@ class Imbecile
   class Parser
 
     def initialize(tokens, rules)
-      start_rules = rules.select {|rule| rule.name == "Start"}
-      start_items = start_rules.map do |rule|
-        Item.new(rule, 0)
+      start_items = rules["Start"].patterns.map do |pattern|
+        Item.new(pattern, 0)
       end
       start_item_set = ItemSet.new(start_items)
       start_item_set.close!
diff --git a/lib/imbecile/parser/item.rb b/lib/imbecile/parser/item.rb
index 0ab3c6f..cf10336 100644
--- a/lib/imbecile/parser/item.rb
+++ b/lib/imbecile/parser/item.rb
@@ -3,24 +3,24 @@ class Imbecile
 
     class Item
 
-      attr_reader :rule
+      attr_reader :pattern
       attr_reader :position
 
-      def initialize(rule, position)
-        @rule = rule
+      def initialize(pattern, position)
+        @pattern = pattern
         @position = position
       end
 
       def next_component
-        @rule.components[@position]
+        @pattern.components[@position]
       end
 
       def hash
-        [@rule, @position].hash
+        [@pattern, @position].hash
       end
 
       def ==(other)
-        @rule == other.rule && @position == other.position
+        @pattern == other.pattern && @position == other.position
       end
 
       def eql?(other)
@@ -28,9 +28,9 @@ class Imbecile
       end
 
       def closed_items
-        if @rule.components[@position].is_a?(Array)
-          @rule.components[@position].map do |rule|
-            Item.new(rule, 0)
+        if @pattern.components[@position].is_a?(Rule)
+          @pattern.components[@position].patterns.map do |pattern|
+            Item.new(pattern, 0)
           end
         else
           []
diff --git a/lib/imbecile/rule.rb b/lib/imbecile/rule.rb
index c89543e..4398248 100644
--- a/lib/imbecile/rule.rb
+++ b/lib/imbecile/rule.rb
@@ -2,16 +2,30 @@ class Imbecile
 
   class Rule
 
+    class Pattern
+
+      attr_reader :components
+
+      attr_reader :code
+
+      def initialize(components, code)
+        @components = components
+        @code = code
+      end
+
+    end
+
     attr_reader :name
 
-    attr_reader :components
+    attr_reader :patterns
 
-    attr_reader :code
-
-    def initialize(name, rule_components, code)
+    def initialize(name)
       @name = name
-      @components = rule_components
-      @code = code
+      @patterns = []
+    end
+
+    def add_pattern(components, code)
+      @patterns << Pattern.new(components, code)
     end
 
   end