anchor.diff:  net_concatenation : LCURLY net_concatenation_value ( COMMA net_concatenation_value )* RCURLY ;
   
   net_concatenation_value
  -  : hierarchical_net_identifier
  -  | hierarchical_net_identifier LSQUARE expression RSQUARE ( LSQUARE expression RSQUARE )*
  -  | hierarchical_net_identifier LSQUARE expression RSQUARE ( LSQUARE expression RSQUARE )* LSQUARE range_expression RSQUARE
  -  | hierarchical_net_identifier LSQUARE range_expression RSQUARE
  +  : hierarchical_identifier
  +  | hierarchical_identifier LSQUARE expression RSQUARE ( LSQUARE expression RSQUARE )*
  +  | hierarchical_identifier LSQUARE expression RSQUARE ( LSQUARE expression RSQUARE )* LSQUARE range_expression RSQUARE
  +  | hierarchical_identifier LSQUARE range_expression RSQUARE
     | net_concatenation
     ;
   
  
positive.code:   ;
  
  variable_concatenation_value
    : hierarchical_variable_identifier
    | hierarchical_variable_identifier LSQUARE expression RSQUARE ( LSQUARE expression RSQUARE )*
    | hierarchical_variable_identifier LSQUARE expression RSQUARE ( LSQUARE expression RSQUARE )* LSQUARE range_expression RSQUARE
    | hierarchical_variable_identifier LSQUARE range_expression RSQUARE
    | variable_concatenation
    ;
  
  
negative.code:   ;
  
  event_control
    : AT_SIGN hierarchical_identifier
    | AT_SIGN LPAREN event_expression RPAREN
    | AT_SIGN MUL
    | AT_SIGN LPAREN MUL RPAREN
  