diff --git a/lib/sorted_containers/sorted_list.rb b/lib/sorted_containers/sorted_list.rb
index 7ae985a..5fb489a 100644
--- a/lib/sorted_containers/sorted_list.rb
+++ b/lib/sorted_containers/sorted_list.rb
@@ -1,13 +1,18 @@
 # frozen_string_literal: true
 
+# The SortedContainers module provides data structures for sorted collections.
 module SortedContainers
   class Error < StandardError; end
 
+  # The SortedList class is a sorted list implementation.
   class SortedList
     DEFAULT_LOAD_FACTOR = 1000
-  
+
     attr_reader :size
-  
+
+    # Initializes a new SortedList object.
+    #
+    # @param iterable [Enumerable] An optional iterable object to initialize the list with.
     def initialize(iterable = [])
       @lists = []
       @maxes = []
@@ -15,7 +20,10 @@ def initialize(iterable = [])
       @size = 0
       update(iterable)
     end
-  
+
+    # Adds a value to the sorted list.
+    #
+    # @param value [Object] The value to add.
     def add(value)
       i = bisect_right(@maxes, value)
       if i == @maxes.size
@@ -30,95 +38,138 @@ def add(value)
       @size += 1
     end
 
+    # Adds a value to the sorted list using the << operator.
+    #
+    # @param value [Object] The value to add.
     def <<(value)
       add(value)
     end
-  
+
+    # Removes a value from the sorted list.
+    #
+    # @param value [Object] The value to remove.
     def remove(value)
       i = bisect_left(@maxes, value)
       return if i == @maxes.size
-  
+
       idx = @lists[i].index(value)
       raise "Value not found: #{value}" unless idx
-  
+
       internal_delete(i, idx)
     end
 
+    # Retrieves the value at the specified index.
+    #
+    # @param index [Integer] The index of the value to retrieve.
+    # @return [Object] The value at the specified index.
     def [](index)
-      raise "Index out of range" if index < 0 || index >= @size
+      raise "Index out of range" if index.negative? || index >= @size
 
       @lists.each do |sublist|
-        if index < sublist.size
-          return sublist[index]
-        else
-          index -= sublist.size
-        end
+        return sublist[index] if index < sublist.size
+
+        index -= sublist.size
       end
     end
 
+    # Deletes the value at the specified index.
+    #
+    # @param index [Integer] The index of the value to delete.
     def delete_at(index)
-      raise "Index out of range" if index < 0 || index >= @size
+      raise "Index out of range" if index.negative? || index >= @size
 
-      @lists.each do |sublist|
+      deleted = false
+      @lists.each_with_index do |sublist, sublist_index|
         if index < sublist.size
-          internal_delete(@lists.index(sublist), index)
-          return
+          internal_delete(sublist_index, index)
+          deleted = true
+          break
         else
           index -= sublist.size
         end
       end
+
+      raise "Index out of range" unless deleted
     end
 
+    # Clears the sorted list, removing all values.
     def clear
       @lists.clear
       @maxes.clear
       @size = 0
     end
 
+    # Checks if the sorted list contains a value.
+    #
+    # @param value [Object] The value to check.
+    # @return [Boolean] True if the value is found, false otherwise.
     def contains(value)
       i = bisect_left(@maxes, value)
       return false if i == @maxes.size
 
       sublist = @lists[i]
       idx = bisect_left(sublist, value)
-      return idx < sublist.size && sublist[idx] == value
+      idx < sublist.size && sublist[idx] == value
     end
 
+    # Converts the sorted list to an array.
+    #
+    # @return [Array] An array representation of the sorted list.
     def to_a
       @lists.flatten
     end
-  
+
     private
-  
+
+    # Performs a left bisect on the array.
+    #
+    # @param array [Array] The array to bisect.
+    # @param value [Object] The value to bisect with.
+    # @return [Integer] The index where the value should be inserted.
     def bisect_left(array, value)
       array.bsearch_index { |x| x >= value } || array.size
     end
-  
+
+    # Performs a right bisect on the array.
+    #
+    # @param array [Array] The array to bisect.
+    # @param value [Object] The value to bisect with.
+    # @return [Integer] The index where the value should be inserted.
     def bisect_right(array, value)
       array.bsearch_index { |x| x > value } || array.size
     end
-  
-    def expand(i)
-      list = @lists[i]
-      if list.size > (@load_factor * 2)
-        half = list.slice!(@load_factor, list.size - @load_factor)
-        @lists.insert(i + 1, half)
-        @maxes[i] = @lists[i].last
-        @maxes.insert(i + 1, half.last)
-      end
+
+    # Expands a sublist if it exceeds the load factor.
+    #
+    # @param sublist_index [Integer] The index of the sublist to expand.
+    def expand(sublist_index)
+      sublist = @lists[sublist_index]
+      return unless sublist.size > (@load_factor * 2)
+
+      half = sublist.slice!(@load_factor, sublist.size - @load_factor)
+      @lists.insert(sublist_index + 1, half)
+      @maxes[sublist_index] = @lists[sublist_index].last
+      @maxes.insert(sublist_index + 1, half.last)
     end
-  
-    def internal_delete(i, idx)
-      @lists[i].delete_at(idx)
-      if @lists[i].empty?
-        @lists.delete_at(i)
-        @maxes.delete_at(i)
+
+    # Deletes a value from a sublist.
+    #
+    # @param sublist_index [Integer] The index of the sublist.
+    # @param idx [Integer] The index of the value to delete.
+    def internal_delete(sublist_index, idx)
+      @lists[sublist_index].delete_at(idx)
+      if @lists[sublist_index].empty?
+        @lists.delete_at(sublist_index)
+        @maxes.delete_at(sublist_index)
       else
-        @maxes[i] = @lists[i].last
+        @maxes[sublist_index] = @lists[sublist_index].last
       end
       @size -= 1
     end
-  
+
+    # Updates the sorted list with values from an iterable object.
+    #
+    # @param iterable [Enumerable] The iterable object to update the list with.
     def update(iterable)
       iterable.each { |item| add(item) }
     end