# File htree/leaf.rb, line 6
    def initialize(version, encoding=nil, standalone=nil)
      init_raw_string
      if /\A[a-zA-Z0-9_.:-]+\z/ !~ version
        raise HTree::Error, "invalid version in XML declaration: #{version.inspect}"
      end
      if encoding && /\A[A-Za-z][A-Za-z0-9._-]*\z/ !~ encoding
        raise HTree::Error, "invalid encoding in XML declaration: #{encoding.inspect}"
      end
      unless standalone == nil || standalone == true || standalone == false
        raise HTree::Error, "invalid standalone document declaration in XML declaration: #{standalone.inspect}"
      end
      @version = version
      @encoding = encoding
      @standalone = standalone
    end