[antlr-interest] Could antlr understand (group)3

[Vidar Håkestad]

Is it possible for antlr to understand a digit as a group operator in addition 
to *, ? and +? This would help in situations where a specific number of 
elements are known.
For example in CSS, a color value may be specified with either three or six 
hex numbers. It would be shorter to write

HEX
  : '0'..'9' | 'a'..'f' | 'A'..'F'
  ;

COLOR
  :  '#' ((HEX)3 | (HEX)6)
  ;

instead of

COLOR
  : '#' ((HEX HEX HEX) | (HEX HEX HEX HEX HEX HEX))
  ;

Vidar