  Creates and activates a constraint that defines a size attribute as equal to another size attribute plus a constant offset.
 
  - parameter leftAnchor: A dimension anchor from a `UIView`, `NSView`, or `UILayoutGuide` object.
- - parameter rest:       A tuple containing an anchor and constant value
  - paramater rightAnchor: A dimension anchor of same type from a `UIView`, `NSView`, or `UILayoutGuide` object.
  - parameter constant:   The offset constant for this relationship.
 

 */


/**
Creates and activates a constraint that defines leftAnchor's attribute as equal to rightAnchor's attribute plus a constant offset.

- parameter leftAnchor: A layout anchor from a `UIView`, `NSView`, or `UILayoutGuide` object.
- parameter pair:       A tuple containing a layout anchor of compatible type and a constant offset.

- returns: The new constraint.
*/
public func |=|(leftAnchor: LayoutAnchor, rest: (rightAnchor: LayoutAnchor, constant: CGFloat)) -> NSLayoutConstraint {
    return install(leftAnchor.constraintEqualToAnchor(rest.rightAnchor, constant: rest.constant))
}

 Creates and activates a constraint that defines leftAnchor's attribute as greater than or equal to rightAnchor's attribute plus a constant offset.

 - parameter leftAnchor: A layout anchor from a `UIView`, `NSView`, or `UILayoutGuide` object.
 - parameter rightAnchor: A layout anchor from a `UIView`, `NSView`, or `UILayoutGuide` object of the same type.
 - parameter constant:  The offset constant for this relationship.

 - returns: The new constraint.
 */
