 
     public var description: String {
         let d = relation.rawValue + object.description
-        if let p = priority {
-            return d + "@\(p)"
-        }
-        return d
+        guard let p = priority else { return d }
+        return "\(d)@\(p)"
     }
 }
 
 // MARK: <relation>
 
 public enum LayoutRelation : String {
-    case Equal = "=="
+    case Equal              = "=="
     case GreaterThanOrEqual = ">="
-    case LessThanOrEqual = "<="
+    case LessThanOrEqual    = "<="
 }
 
 // MARK: <objectOfPredicate>

        }

        predicates = pred_part.map { e in
            switch e {
            case .Predicate(let p): return p
            default:                fatalError("Error")
            }
        }
    }
}

    }

    private var relatedViews: [LayoutViewName] {
        return [view] + predicates.flatMap { e -> LayoutViewName? in
            switch e.object {
            case .View(let v): return v
            default:           return nil
            }
        }
    }
