 
     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>


    public var description: String {
        switch self {
        case Constant(let n): return "\(n)"
        case View(let view):  return view.description
        }
    }

        }

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