 	case Line
 	case Cat(Document, Document)
 	case FlatAlt(Document, Document)
+	case Union(Document, Document)
 }
 
 // MARK: Document : DocumentType


extension DocumentType {
	public static var space: Self { return .char(" ") }
}

// MARK: - extension CollectionType where Index: RandomAccessIndexType

	static var hardline: Self { get }
	static var line: Self { get }
	static var linebreak: Self { get }
	static func union(x: Self, _ y: Self) -> Self
	
	func beside(other: Self) -> Self
}

