anchor.diff:  	(  permutable  |  portRef  )*
   	')';
   
  -not : '(not'
  +not_ : '(not'
   	booleanExpression
   	')';
   
  
positive.code: 	unitExponent
  	')';
  
  and : '(and'
  	(  booleanExpression  )*
  	')';
  
  
negative.code: 	curve
  	')';
  
  or_ : '(or'
  	(  booleanExpression  )*
  	')';
  
  