 /**
  * ConstraintAttributes is an options set that maps to NSLayoutAttributes.
  */
-struct ConstraintAttributes: RawOptionSet {
+struct ConstraintAttributes: RawOptionSetType {
 
     var value: UInt
+    var boolValue: Bool {
+        return self.value != 0
+    }
 
     init(_ value: UInt) {
         self.value = value

        return attrs
    }
}
@assignment func += (inout left: ConstraintAttributes, right: ConstraintAttributes) {
    left = (left | right)
}
@assignment func -= (inout left: ConstraintAttributes, right: ConstraintAttributes) {
    left = ConstraintAttributes(left.toRaw() & ~right.toRaw())
}

/**

        let layoutTo: View? = self.toItem.view
        
        // get layout relation
        let layoutRelation: NSLayoutRelation = (self.relation != nil) ? self.relation!.layoutRelation : .Equal
        
        for layoutFromAttribute in layoutFromAttributes {
            // get layout to attribute
