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From: David Abrahams (dave_at_[hidden])
Date: 2008-02-01 11:33:17

on Fri Feb 01 2008, Eric Niebler <> wrote:

> Hansi Hansi wrote:
>> I have looked another time to the implementation of the histogram. If
>> we want to implement it in the same class density, than it is needed
>> to provide default parameter for density_cache_size or min/max. Is it
>> possible to ensure that either density_cache_size or min/max is
>> provided as parameter? Sorry for the question but I'm not so familiar
>> with parameters...
> Yes, it's possible. IIRC, a parameter pack is a valid MPL sequence, so
> you can us MPL algorithms to detect the presence or absence of any
> parameter.

  boost::parameter::binding< argpack, tag::parametername, void >::type

will tell you. If the result is void, the parameter wasn't supplied.

Dave Abrahams
Boost Consulting

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