EBNF notation for dice roller

attack roll = [multiply roll result], [digits], 'd', numeral ;
roll notation = attack roll, {[operator, ( attack roll | digits )]}, [negate high or low roll], [white space, all characters] ;

digits = '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9' ;
(* Note: By using regular expressions, digits can be expressed by / \d+ /. *) ;
multiply roll result = digits, '#' ;
negate high or low roll = '-H' | '-L';
operator = ':+'
         | ':-'
         | ':/'
         | ':*' ;
white space = ? white space characters ? ;
all characters = ? all visible characters ? ;

(* Syntax example: 2#3d6+d6/2+3*4-L Attack this! *) ;