Re: [boost] Accumulators review

In the tutorial it says: " Even the extractors can accept named parameters. In a bit, we'll see a situation where that is useful." But I can't find any further mention of extractors with named parameters, I ask because I believe it may be indeed be useful - for example a student's t test could defer requiring the acceptable risk level until the extractor is actually called - so the same test could be conducted multiple times with different risk levels for example just by calling the extractor multiple times. One other thing I've missed is the ability to "reset" an accumulator so it can be used more than once. Is this possible? Potentially it might save quite a bit of construction cost in some cases? Thanks, John.