Лексическая структура выражения
[28] ExprToken ::= '(' | ')' | '[' | ']' | '.' | '..' | '@' | ',' | '::' | | | | | | | | [29] Literal ::= '"' [^"]* '"' | "'" [^']* "'" [30] Number ::= ('.' ?)? | '.' [31] Digits ::= [0-9]+ [32] Operator ::= | | '/' | '//' | '|' | '+' | '-' | '=' | '!=' | '<' | '<=' | '>' | '>=' [33] OperatorName ::= 'and' | 'or' | 'mod' | 'div' [34] MultiplyOperator ::= '*' [35] FunctionName ::= - [36] VariableReference ::= '$' [37] NameTest ::= '*' | ':' '*' | [38] NodeType ::= 'comment' | 'text' | 'processing-instruction' | 'node' [39] ExprWhitespace ::=
