anchor.diff:  
           static member (+) (constrain, constrain2) =
               match (constrain, constrain2) with
  -            | (Unconstrained, Unconstrained) -> Unconstrained
  +            | (Unconstrained, Unconstrained) -> constrain // OPTIMIZATION: elide Constraint ctor
               | (_, Unconstrained) -> constrain
               | (Unconstrained, _) -> constrain2
               | (_, _) -> Constraints [|constrain; constrain2|]
  
positive.code: 
      /// The default particle emitter.
      type [<NoEquality; NoComparison>] Emitter<'a when 'a :> Particle and 'a : struct> =
          { Life : Life
            Body : Body
            mutable ParticleIndex : int // operates as a ring-buffer
            Particles : 'a array // operates as a ring-buffer
            Initializer : int64 -> Constraint -> 'a Emitter -> 'a
            Behaviors : Behaviors
            Constraint : Constraint
            Rate : single
            Id : Guid }
  
          static member private computeLiveness time emitter =
              let length = emitter.Particles.Length
              let mutable index = 0
              let mutable result = Dead
              while (match result with Live -> false | Dead -> true) && index < length do
                  let particle = &emitter.Particles.[index]
                  match Life.getLiveness time particle.Life with
                  | Live -> result <- Live
                  | Dead -> index <- inc index
              result
  
          static member private emit time constrain emitter =
              let particleIndex = if emitter.ParticleIndex >= emitter.Particles.Length then 0 else inc emitter.ParticleIndex
  
negative.code:             (single time - single life.StartTime) / single life.LifeTime
  
          /// The liveness of the instance.
          /// OPTIMIZATION: avoiding use of Liveness type to avoid its constructor calls.
          static member getLiveness (time : int64) life =
              let localTime = time - life.StartTime
              life.LifeTime < localTime
  
      /// Describes the body of an instance value.
      type [<NoEquality; NoComparison; Struct>] Body =
  