   let first = vfirst!
   let last = vlast!
 
-  StayConstraint(variable: last, strength: STRONG_DEFAULT)
+  let _ = StayConstraint(variable: last, strength: STRONG_DEFAULT)
   let edit = EditConstraint(variable: first, strength: PREFERRED)
   let plan = planner.extractPlanFromConstraints([edit])
   for i in 0..<100 {

    vsrc = Variable(name: "src", value: i)
    vdst = Variable(name: "dst", value: i)
    dests.append(vdst!)
    StayConstraint(variable: vsrc!, strength: NORMAL)
    ScaleConstraint(src: vsrc!, scale: scale, offset: offset, dest: vdst!,
        strength: REQUIRED)
  }

  let src = vsrc!

  for i in 0...n {
    let v = Variable(name: "v", value: 0)
    if let p = prev {
      let _ = EqualityConstraint(v1: p, v2: v, strength: REQUIRED)
    }
    if i == 0 {
      vfirst = v
