Add bin and edit workflow

bin/gems/rake-13.4.2/lib/rake/linked_list.rb

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+# frozen_string_literal: true
+module Rake
+
+  # Polylithic linked list structure used to implement several data
+  # structures in Rake.
+  class LinkedList
+    include Enumerable
+    attr_reader :head, :tail
+
+    # Polymorphically add a new element to the head of a list. The
+    # type of head node will be the same list type as the tail.
+    def conj(item)
+      self.class.cons(item, self)
+    end
+
+    # Is the list empty?
+    # .make guards against a list being empty making any instantiated LinkedList
+    # object not empty by default
+    # You should consider overriding this method if you implement your own .make method
+    def empty?
+      false
+    end
+
+    # Lists are structurally equivalent.
+    def ==(other)
+      current = self
+      while !current.empty? && !other.empty?
+        return false if current.head != other.head
+        current = current.tail
+        other = other.tail
+      end
+      current.empty? && other.empty?
+    end
+
+    # Convert to string: LL(item, item...)
+    def to_s
+      items = map(&:to_s).join(", ")
+      "LL(#{items})"
+    end
+
+    # Same as +to_s+, but with inspected items.
+    def inspect
+      items = map(&:inspect).join(", ")
+      "LL(#{items})"
+    end
+
+    # For each item in the list.
+    def each
+      current = self
+      while !current.empty?
+        yield(current.head)
+        current = current.tail
+      end
+      self
+    end
+
+    # Make a list out of the given arguments. This method is
+    # polymorphic
+    def self.make(*args)
+      # return an EmptyLinkedList if there are no arguments
+      return empty if !args || args.empty?
+
+      # build a LinkedList by starting at the tail and iterating
+      # through each argument
+      # inject takes an EmptyLinkedList to start
+      args.reverse.inject(empty) do |list, item|
+        list = cons(item, list)
+        list # return the newly created list for each item in the block
+      end
+    end
+
+    # Cons a new head onto the tail list.
+    def self.cons(head, tail)
+      new(head, tail)
+    end
+
+    # The standard empty list class for the given LinkedList class.
+    def self.empty
+      self::EMPTY
+    end
+
+    protected
+
+    def initialize(head, tail=EMPTY)
+      @head = head
+      @tail = tail
+    end
+
+    # Represent an empty list, using the Null Object Pattern.
+    #
+    # When inheriting from the LinkedList class, you should implement
+    # a type specific Empty class as well. Make sure you set the class
+    # instance variable @parent to the associated list class (this
+    # allows conj, cons and make to work polymorphically).
+    class EmptyLinkedList < LinkedList
+      @parent = LinkedList
+
+      def initialize
+      end
+
+      def empty?
+        true
+      end
+
+      def self.cons(head, tail)
+        @parent.cons(head, tail)
+      end
+    end
+
+    EMPTY = EmptyLinkedList.new
+  end
+end