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    digit = "0123456789".
    space = 32 [noKeep].

    printable = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789!,+-/\*~=@%&?|<>[]{}()^;#:.$_' ".
    endOfFileCharacter = 256.
    lineEnd = 10 [noKeep].
    all = printable | endOfFileCharacter.

    test = $0 .. $9.

    EndOfFile {endOfFileCharacter}
        -> => EndOfFile.

    WhiteSpace {all - space}
       -> space+.

    Integer {all - digit}
        -> digit+ => Integer.

    Comment {all}
        -> $/ [noKeep] {all - $/} #syntaxError: ["// is a comment, / alone is not valid"]
        -> $/ [noKeep] $/ [noKeep]
                (printable [noKeep] - lineEnd [noKeep])*
            (
                lineEnd [noKeep] |
                {endOfFileCharacter}
            ).