anchor.diff:  
   ; PROCURA RETROCESSO MAC MRV
   
  -; Search for regression solving the CSP used by MAC (Maintain Arc Consistency)
  -; function and applying MRV heuristic model.
  +; Uses the MAC heurisitic to propagate constrains in order to reduce 
  +; domain sizes and speed up the solving process
   
   (defun procura-retrocesso-mac-mrv (psr)
   	(let ((testesTotais 0) (res nil) (res1 nil) (var nil) (inf nil))
  
positive.code: 
  ; EXPANDS LIST
  
  ; Expands the list in arc iteratively.
  
  (defun ExpandsList (psr lista inferencia)
  	(let (
  
negative.code: 
  ; EXPLORE PSR CONSTRAINS
  
  ; Finds all the variables which are not involved in any constrain, if any.
  
  (defun ExplorePSRconstr (psr)
  	(let ( (lstaux (psr-listconstrains psr))
  