问题
With separate Lexer and Parser ...
class YamlLexical extends StdLexical with YamlTokens with RegexParsers {...
object YamlParser extends StdTokenParsers with YamlTokens with PackratParsers {...
... how to get the position of the parsed string into AST classes?
(... positioned(elem(...)) * ... )^^ { ... => List( Ast(startpos, parsedtext, ... subnodes ... ), ... )}
回答1:
The type of positioned is
def positioned[T <: Positional](p: ⇒ Parser[T]): Parser[T]
which means that the parsed elements must extend Positional. So, for example, YamlLexical should be:
class YamlLexical extends Positional
in that way, any parsed element will automatically have a pos which records the position in which it was parsed.
来源：https://stackoverflow.com/questions/20919068/using-positional-and-positioned-in-scala-parser-combinators