anchor.diff:                  let (outputs, target) = Behavior<'a, 'b>.run time constrain this (targetObj :?> 'a)
                   (outputs, target :> obj)
               member this.RunMany time constrain targetsObj =
  -                let (outputs, targets) = Behavior<'a, 'b>.runMany time constrain this (targetsObj :?> 'a SegmentedArray)
  -                (outputs, targets :> obj)
  +                Behavior<'a, 'b>.runMany time constrain this (targetsObj :?> 'a SegmentedArray)
   
       /// A composition of behaviors.
       type [<NoEquality; NoComparison>] Behaviors =
  
positive.code:                         let body = &bodies.[i]
                          body.LinearVelocity <- body.LinearVelocity + gravity
                          i <- inc i
                      (Output.empty, bodies)
                  | Attractor (position, radius, force) ->
                      let mutable i = 0
                      while i < dec bodies.Length do
  
negative.code:                 body.Position <- body.Position + body.LinearVelocity
                  body.Angles <- body.Angles + body.AngularVelocity
                  i <- inc i
  
          /// Constrain bodies.
          let rec constrain c (bodies : Body SegmentedArray) =
  