vendored parslet, deemed stable enough and better without dependency

lib/parslet/scope.rb

@@ -0,0 +1,42 @@
+class Parslet::Scope
+  # Raised when the accessed slot has never been assigned a value. 
+  #
+  class NotFound < StandardError
+  end
+  
+  class Binding
+    attr_reader :parent
+    
+    def initialize(parent=nil)
+      @parent = parent
+      @hash = Hash.new
+    end
+    
+    def [](k)
+      @hash.has_key?(k) && @hash[k] ||
+        parent && parent[k] or 
+        raise NotFound
+    end
+    def []=(k,v)
+      @hash.store(k,v)
+    end
+  end
+  
+  def [](k)
+    @current[k]
+  end
+  def []=(k,v)
+    @current[k] = v
+  end
+  
+  def initialize
+    @current = Binding.new
+  end
+  
+  def push
+    @current = Binding.new(@current)
+  end
+  def pop
+    @current = @current.parent
+  end
+end