anchor.diff:  . Mark all _the rest_ as garbage
   
   
  -GC Principles: References Count
  --------------------------------
  +(Too) simple solution: References Counting
  +------------------------------------------
   
   Counting the references to an object may easily be automated.
  +(E.g. Python prior v2)
   
   [graphviz,,fdp]
   -----
  
positive.code: -----
  
  
  GC Principles: References Count
  -------------------------------
  
  But:
  
  
negative.code: * triggers a young collection when full
  * objects surviving young collection are copied to one of the survivor spaces
  * then the whole area is considered empty (no need to explicitely delete all unmarked objects)
  * = +Mark and Copy+ (thanks to the copy, no need to +sweep+ and the +compact+ is done on the fly)
  
  
  GC Principles: Memory Pools
  