anchor.diff:      ;
   
   selectorSequence
  -    : ( typeSelector | universal ) ( id | className | attrib | pseudo | negation | interpolation ( variableName | Percentage )? | parent )*
  -    | ( id | className | attrib | pseudo | negation | interpolation ( variableName | Percentage )? | parent )+
  +    : ( typeSelector | universal ) ( id | className | attrib | pseudo | negation | interpolation ( variableName | Percentage )? | parentRef )*
  +    | ( id | className | attrib | pseudo | negation | interpolation ( variableName | Percentage )? | parentRef )+
       ;
   
   id
  
positive.code:     ;
  
  ifExpression
      : If Lparen ( expression | parent ) Comma value Comma value Rparen measurment? ws prio?
      ;
  
  
  
negative.code:     ;
  
  interpolation
      : namespace_? Hash BlockStart namespace_? ( ifExpression | value | parentRef ) BlockEnd measurment?
      ;
  
  parentRef
      : Amp
      ;
  
  