anchor.diff:  head's `:strobe`
   https://github.com/brunchboy/afterglow/blob/master/doc/fixture_definitions.adoc#function-specifications[function].
   The assignment values they return are either a percentage value, a
  -dynamic parameter which will resolve to a percentage value, or `nil`,
  -meaning no assignment should take place.
  +<<parameters#dynamic-parameters,dynamic parameter>> which will resolve
  +to a percentage value, or `nil`, meaning no assignment should take
  +place.
   
   When the assignment is resolved,
   http://deepsymmetry.org/afterglow/doc/afterglow.effects.channel.html#var-function-assignment-resolver[function-assignment-resolver]
  
positive.code: Channel assigners have a `kind` of `:channel`, and their `target-id`
  is a keyword of the form `:u1a234` which would represent an assignment
  to universe `1`, address `234`. The assignment values they return are
  either a valid DMX data value (see next paragraph), a dynamic
  parameter which will resolve to a valid DMX data value, or `nil`,
  meaning no assignment should take place.
  
  
  [[dmx-values]] The DMX data value is a number in the range `[0-256)`.
  
negative.code: Aim Assigners
  ^^^^^^^^^^^^^
  
  Aim assigners have a `kind` of `:aim`, and their `target-id` is a
  keyword of the form `:i17` which would represent an assignment to the
  fixture or head with ID 17. The assignment values they return are
  either a `javax.vecmath.Point3d`, a
  <<parameters#aim-parameters,dynamic parameter>> which will resolve to
  a `Point3d` object, or `nil`, meaning no assignment should take place.
  
  When the assignment is resolved, the point identifies the precise
  location in the <<show_space#show-space,frame of reference of the
  