/* An EBNF grammar for EBNF */
    [1] ebnf        ::= (declaration | rule)*

    [2] declaration ::= '@terminals' | pass

    [3] rule        ::= LHS expression

    # Use a terminal to match the identifier, rule name and assignment due to
    # confusion between the identifier RANGE

    [4] expression  ::= alt

    [5] alt         ::= seq ('|' seq)*

    [6] seq         ::= diff+

    [7] diff        ::= postfix ('-' postfix)?

    [8] postfix     ::= primary POSTFIX?

    [9] primary     ::= HEX
                    |   SYMBOL
                    |   RANGE
                    |   O_RANGE
                    |   STRING1
                    |   STRING2
                    |   '(' expression ')'

    [10] pass       ::= '@pass' expression

    @terminals

    [11] LHS        ::= ('[' SYMBOL+ ']')? SYMBOL "::="

    [12] SYMBOL     ::= ([a-z] | [A-Z] | [0-9] | "_" | ".")+

    [13] HEX        ::= '#x' ([0-9]|[a-f]|[A-F])+

    # Range is any combination of R_CHAR '-' R_CHAR or R_CHAR+
    [14] RANGE      ::= '[' ((R_BEGIN (HEX | R_CHAR)) | (HEX | R_CHAR))+ ']'

    # Range is any combination of R_CHAR '-' R_CHAR or R_CHAR+ preceded by ^
    [15] O_RANGE    ::= '[^' ((R_BEGIN (HEX | R_CHAR)) | (HEX | R_CHAR))+ ']'

    # Strings are unescaped Unicode, excepting control characters and hash (#)
    [16] STRING1    ::= '"' (CHAR - '"')* '"'

    [17] STRING2    ::= "'" (CHAR - "'")* "'"

    [18] CHAR       ::= HEX
                      | [#x20#x21#x22]
                      | [#x24-#x00FFFFFF]

    [19] R_CHAR     ::= CHAR - ']'

    [20] R_BEGIN    ::= (HEX | R_CHAR) "-"

    # Should be able to do this inline, but not until terminal regular expressions are created automatically
    [21] POSTFIX    ::= [?*+]

    [22] PASS       ::= ( [#x00-#x20]
                        | ( '#' | '//' ) [^#x0A#x0D]*
                        | '/*' (( '*' [^/] )? | [^*] )* '*/'
                        | '(*' (( '*' [^)] )? | [^*] )* '*)'
                        )+

    # Should be able to do this inline, but not until terminal regular expressions are created automatically
    @pass           PASS