bbnf.bbnf

identifier = /[_a-zA-Z][_a-zA-Z0-9-]*/ ;

literal = "\"" , /(\\.|[^"\\])*/  , "\""
        | "'"  , /(\\.|[^'\\])*/  , "'"
        | "`"  , /(\\.|[^`\\])*/  , "`" ;

big_comment = ( "/*" , /[^\*]*/ , "*/" ) ?w ;
comment = ( "//" , /.*/ ) ?w ;

regex = "/" , /(\\.|[^\/])+/ , "/" ;

lhs = identifier ;

term = "ε"
     | identifier
     | literal 
     | regex
     | "(" , rhs ?w , ")" 
     | "[" , rhs ?w , "]"
     | "{" , rhs ?w , "}" ;


factor = big_comment ? , (
      term ?w , "?w"
    | term ?w , "?"
    | term ?w , "*"
    | term ?w , "+"
    | term  
) , big_comment ? ;

binary_operators = "<<" | ">>" | "-" ;

binary_factor = factor , ( binary_operators ?w , factor ) * ;

concatenation = ( binary_factor ?w , "," ? ) + ;
alternation = ( concatenation ?w , "|" ? ) + ;

rhs = alternation ;

rule = lhs, "=" ?w, rhs ?w, ( ";" | "." ) ;

grammar =  ( comment ? , rule ?w , comment ? ) * ;