Parser combinators info

I am using parsing combinators in scala If I have recursive parser:

val uninterestingthing开发者_高级运维s = ".".r

val parser = "(?ui)(regexvalue)".r | (uninterestingthings~>parser)

How can I check how many characters of input my parser consumed?

There is a positioned combinator that (to quote its documentation) "decorates a parser's result with the start position of the input it consumed."