scanner

    //Note: scanners don't use stack and node, just read/look and keep/noKeep.
    //Note: Space = 32; Tab = 9; Cr = 13; Lf = 10; Ff = 12.

    attribute defaults "noStack" "read" "noNode" "keep".
    output "All". //One of All, Smalltalk, Ruby, C++, C++98, or Java

    uppercase = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".
    lowercase = "abcdefghijklmnopqrstuvwxyz".
    letter = uppercase | lowercase | "_".
    digit = "0123456789".
    operator = "!,+-/\*~=@%&?|<>".
    singleQuote = "'".
    doubleQuote = '"'.

    tab = 9 [noKeep].
    carriageReturn = 13 [noKeep].
    lineFeed = 10 [noKeep].
    formFeed = 12 [noKeep].
    blank = 32 [noKeep]. //Or "$ [keep]" which is hard to see after the $...

    lineEnd = carriageReturn | lineFeed  | formFeed.
    space = blank | tab | lineEnd.
    others = "[]{}()^;#:.$_" | singleQuote | doubleQuote | space.

    slantedSingleQuote = 96.
    slantedDoubleQuote = 147 | 148. 

    printable = letter | digit | operator | others | slantedSingleQuote | slantedDoubleQuote.
    endOfFileCharacter = 256.
    all = printable | endOfFileCharacter.

    EndOfFile {endOfFileCharacter}
        -> => EndOfFile.
    EndOfFile {endOfFileCharacter}
        -> => '-|'.

    WhiteSpace {all - space}
       -> space+.

    IdentifierOrSymbol {all - (letter | digit | $:)}
        -> letter (letter | digit | $: )* => walkIdentifier:
        -> $# [noKeep] letter (letter | digit | $: )* => walkSymbol:.

    SingleQuotedStringOrSymbol {all - $'}
        -> $' [noKeep] ((printable - $') [keep] | $' [noKeep] $' [keep])* $' [noKeep] => walkString:
    -> $' [noKeep] ((printable - $') [keep] | $' [noKeep] $' [keep])* {endOfFileCharacter} #syntaxError: ["missing end quote for single quoted string"] => walkString:
        -> $# [noKeep] $' [noKeep] ((printable - $') [keep] | $' [noKeep] $' [keep])* $' [noKeep] => walkSymbol:
    -> $# [noKeep] $' [noKeep] ((printable - $') [keep] | $' [noKeep] $' [keep])* {endOfFileCharacter} #syntaxError: ["missing end quote for single quoted string"] => walkSymbol:.

    DoubleQuotedStringOrSymbol {all - $"}
        -> $" [noKeep] ((printable - $") [keep] | $" [noKeep] $" [keep])* $" [noKeep] => walkString:
        -> $" [noKeep] ((printable - $") [keep] | $" [noKeep] $" [keep])* {endOfFileCharacter} #syntaxError: ["missing end quote for double quoted string"] => walkString:
        -> $# [noKeep] $" [noKeep] ((printable - $") [keep] | $" [noKeep] $" [keep])* $" [noKeep] => walkSymbol:
        -> $# [noKeep] $" [noKeep] ((printable - $") [keep] | $" [noKeep] $" [keep])* {endOfFileCharacter} #syntaxError: ["missing end quote for double quoted string"] => walkSymbol:.

    Brackets {all}
        -> $( => OpenRound
        -> $) => CloseRound
        -> ${ => OpenCurly
        -> $} => CloseCurly
        -> $[ => OpenSquare
        -> $] => CloseSquare.

    RegularExpressionOperator1 {all}
        -> $| => Or
        -> $& => And
        -> $* => Star
        -> $+ => Plus
        -> $? => QuestionMark
        -> $. $. => DotDot.

    RegularExpressionOperator2 {all - $>}
        -> $- => Minus.

    Punctuation {all - $.}
        -> $. => Dot.

    Arrow1 {all - $>}
        -> $= => Equals .

    Arrow2 {all}
        -> $- $> => RightArrow
        -> $= $> => FatRightArrow.

    Character {all}
        -> $$ [noKeep] printable [keep] => walkCharacter:.

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

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