anchor.diff:  
       /// Describes the life of an instance value.
       /// OPTIMIZATION: LifeTimeOpt uses 0L to represent infinite life.
  -    /// OPTIMIZATION: avoids use of Liveness type to avoid its constructor calls.
  +    /// OPTIMIZATION: doesn't use Liveness type to avoid its constructor calls.
       type [<NoEquality; NoComparison; Struct>] Life =
           { StartTime : int64
             LifeTimeOpt : int64 }
  
positive.code:             member this.Run time constrain =
                  let (emitter, output) = Emitter<'a>.run time constrain this
                  (emitter :> Emitter, output)
              end
  
      /// A particle system.
  
negative.code:               Body = { Position = v2Zero; LinearVelocity = v2Zero; Rotation = 0.0f; AngularVelocity = 0.0f; Gravity = v2 0.0f -9.81f }
                Image = image
                Rate = rate
                Id = Gen.id }
  