@before {
        self.statementTerminator = @";";
        self.singleLineCommentMarker = nil;
        self.multiLineCommentStartMarker = @"(:";
        self.multiLineCommentEndMarker = @":)";
		self.blockStartMarker = @"{";
		self.blockEndMarker = @"}";
        self.braces = @"( ) [ ] < > (: :)";

        PKTokenizer *t = self.tokenizer;
        [t.symbolState add:@"//"];
        [t.symbolState add:@".."];
        [t.symbolState add:@":="];
        [t.symbolState add:@"!="];
        [t.symbolState add:@"::"];
        [t.symbolState add:@"<="];
        [t.symbolState add:@"=>"];
        [t.symbolState add:@"(:"];
        [t.symbolState add:@":)"];

        NSMutableCharacterSet *cs = [[NSCharacterSet alphanumericCharacterSet] mutableCopy];
        [cs addCharactersInString:@"_"];
        [t.delimitState addStartMarker:@"$" endMarker:@"" allowedCharacterSet:cs];
        [t setTokenizerState:t.delimitState from:'$' to:'$'];

        [t setTokenizerState:t.wordState from:'_' to:'_'];
        [t.wordState setWordChars:YES from:'-' to:'-'];
        [t.wordState setWordChars:YES from:'_' to:'_'];
        [t.wordState setWordChars:YES from:'.' to:'.'];
        [t.wordState setWordChars:NO from:'\\'' to:'\\''];

        [t setTokenizerState:t.symbolState from:'-' to:'-'];

        [t setTokenizerState:t.numberState from:'.' to:'.'];

        [t setTokenizerState:t.numberState from:'#' to:'#'];
        t.numberState.allowsScientificNotation = YES;

        [t setTokenizerState:t.symbolState from:'/' to:'/'];

        // setup comments
        t.commentState.reportsCommentTokens = YES;
        [t.commentState addMultiLineStartMarker:@"(:" endMarker:@":)"];
        [t setTokenizerState:t.commentState from:'(' to:'('];
        [t setTokenizerState:t.commentState from:':' to:':'];
        [t.commentState setFallbackState:t.symbolState from:'(' to:'('];
        [t.commentState setFallbackState:t.symbolState from:':' to:':'];
}

expr = token*;
token = colon | assign | eq | ne | dot | lt | gt | separators | operators | star | braces | comment | variable | keyword | builtin | functionName | axisName | string | number | ncName;

comment         = Comment;

colon           = ':';
assign          = ':=';
eq              = '=';
ne              = '!=';
dot             = singleDot | doubleDot;
singleDot       = '.';
doubleDot       = '..';
lt              = '<';
gt              = '>';

separators      = slash | doubleSlash | axisSep;
    slash           = '/';
    doubleSlash     = '//';
    axisSep         = '::';

operators = or | and | div | mod | pipe | comma | plus | minus | question | le | ge;
    or = 'or';
    and = 'and';
    div = 'div';
    mod = 'mod';
    pipe = '|';
    comma = ',';
    plus = '+';
    minus = '-';
    question = '?';
    le = '<=';
    ge = '>=';

star = '*';

braces = openParen | closeParen | openSquare | closeSquare | openCurly | closeCurly | symbol;
    openParen = '(';
    closeParen = ')';
    openSquare = '[';
    closeSquare = ']';
    openCurly = '{';
    closeCurly = '}';
    symbol = Symbol;
    
variable = %{'$', ''};

keyword = function | declare | if | then | else | switch | case | default | for | at | in | let | to | where | order | by | ascending | descending | return | some | every | satisfies | intersect | union | except | valLt | valGt | valLe | valGe | valEq | valNe;
    function = 'function';
    declare = 'declare';
    if = 'if';
    then = 'then';
    else = 'else';
    switch = 'switch';
    case = 'case';
    default = 'default';
    for = 'for';
    at = 'at';
    in = 'in';
    let = 'let';
    to = 'to';
    where = 'where';
    order = 'order';
    by = 'by';
    ascending = 'ascending';
    descending = 'descending';
    return = 'return';
    some = 'some';
    every = 'every';
    satisfies = 'satisfies';
    intersect = 'intersect';
    union = 'union';
    except = 'except';
    valEq = 'eq';
    valNe = 'ne';
    valLt = 'lt';
    valGt = 'gt';
    valLe = 'le';
    valGe = 'ge';

builtin = commentSym | textSym | piSym | node | booleanLiteral;
    commentSym  = 'comment';
    textSym = 'text';
    piSym = 'processing-instruction';
    node = 'node';

    booleanLiteral = true | false;
        true = 'true';
        false = 'false';
        
functionName
    = absFn
    | avgFn
    | booleanFn
    | ceilingFn
    | compareFn
    | concatFn
    | containsFn
    | countFn
    | dataFn
    | distinctValuesFn
    | emptyFn
    | endsWithFn
    | existsFn
    | floorFn
    | headFn
    | idFn
    | indexOfFn
    | insertBeforeFn
    | langFn
    | lastFn
    | localNameFn
    | lowerCaseFn
    | matchesFn
    | maxFn
    | minFn
    | nameFn
    | namespaceUriFn
    | normalizeSpaceFn
    | normalizeUnicodeFn
    | notFn
    | numberFn
    | positionFn
    | removeFn
    | replaceFn
    | reverseFn
    | roundFn
    | startsWithFn
    | stringFn
    | stringJoinFn
    | stringLengthFn
    | subsequenceFn
    | substringFn
    | substringAfterFn
    | substringBeforeFn
    | sumFn
    | tailFn
    | traceFn
    | translateFn
    | trimSpaceFn
    | titleCaseFn
    | upperCaseFn
    ;

absFn = 'abs';
avgFn = 'avg';
booleanFn = 'boolean';
ceilingFn = 'ceiling';
compareFn = 'compare';
concatFn = 'concat';
containsFn = 'contains';
countFn = 'count';
dataFn = 'data';
distinctValuesFn = 'distinct-values';
emptyFn = 'empty';
endsWithFn = 'ends-with';
existsFn = 'exists';
floorFn = 'floor';
headFn = 'head';
idFn = 'id';
indexOfFn = 'index-of';
insertBeforeFn = 'insert-before';
langFn = 'lang';
lastFn = 'last';
localNameFn = 'local-name';
lowerCaseFn = 'lower-case';
matchesFn = 'matches';
maxFn = 'max';
minFn = 'min';
nameFn = 'name';
namespaceUriFn = 'namespace-uri';
normalizeSpaceFn = 'normalize-space';
normalizeUnicodeFn = 'normalize-unicode';
notFn = 'not';
numberFn = 'number';
positionFn = 'position';
removeFn = 'remove';
replaceFn = 'replace';
roundFn = 'round';
reverseFn = 'reverse';
startsWithFn = 'starts-with';
stringFn = 'string';
stringJoinFn = 'string-join';
stringLengthFn = 'string-length';
subsequenceFn = 'subsequence';
substringFn = 'substring';
substringAfterFn = 'substring-after';
substringBeforeFn = 'substring-before';
sumFn = 'sum';
tailFn = 'tail';
traceFn = 'trace';
translateFn = 'translate';
trimSpaceFn = 'trim-space';
titleCaseFn = 'title-case';
upperCaseFn = 'upper-case';

axisName = atSym | 'ancestor' | 'ancestor-or-self' | 'attribute' | 'child' | 'descendant' | 'descendant-or-self' | 'following' | 'following-sibling' | 'namespace' | 'parent' | 'preceding' | 'preceding-sibling' | 'self';
    atSym = '@';

string = QuotedString;
number = Number;

ncName = Word;
/*attrNCName = Word;*/