anchor.diff:  
   ; MAC (Maintain Arc Consistency)
   
  -; This functions propagates variables restrictions of the psr.
  +; Ensures that the arc consistency for a given variable is maintained
   
   (defun MAC (psr var)
   	(let ((testesTotais 0) 
  
positive.code: 
  ; PROCURA RETROCESSO MAC MRV
  
  ; Search for regression solving the CSP used by MAC (Maintain Arc Consistency)
  ; function and applying MRV heuristic model.
  
  (defun procura-retrocesso-mac-mrv (psr)
  	(let ((testesTotais 0) (res nil) (res1 nil) (var nil) (inf nil))
  
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))
  