anchor.diff:  
   A = B + C * A
   
  +----
   Derivación izquierda (Left Most Derivation)
  -+++++++++++++++++++++++++++++++++++++++++++
   
   <Asignacion> => <Id> = <Expresion>
   				=> A = <Expresion> + <Term>
  
positive.code:               	=> A = B + C * A
                	
  Derivación derecha (Right Most Derivation)
  +++++++++++++++++++++++++++++++++++++++++++
  
  <Asignacion> => <Id> = <Expresion>
  				=> <Id> = <Expresion> + <Term>
  
negative.code:       			=> <Id> = <Term> + C * A
        			=> <Id> = <Id> + C * A
        			=> <Id> = B + C * A
        			=>  A = B + C * C