Re: [Boost-users] [Multi-Index] has_index<BMI,TAG> meta-function

On Fri, Jul 17, 2009 at 9:07 AM, Joaquin M Lopez Munoz wrote:

Dominique Devienne writes:

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On Tue, Jul 14, 2009 at 5:49 PM, JOAQUIN M. LOPEZ MUÑOZ

One last question tonight :)

Sorry it's been a little later than that. I've been offline for the last couple of days.

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Similarly to how I can now statically enable/disable code based on which index is implemented by a BMI, can one also change that code based on whether the index is unique vs non-unique? Or ordered vs hashed? [...]

Use index_specifier_type_list instead of index_type_list (differences explained at http://tinyurl.com/nwe27r ) and resort to something like this:

 template<typename IndexSpecifier>  struct is_unique_index:boost::mpl::false_{};

 template  struct is_unique_index<    boost::multi_index::ordered_unique  >:boost::mpl::true_{};

 template  struct is_unique_index<    boost::multi_index::hashed_unique  >:boost::mpl::true_{};

and similarly for ordered vs hashed.

Thanks. Partial specialization I understand at least :) Although that's the first time I see the specialization having more template arguments than the base template, and that threw me off initially, but I see there's still a single template argument in is_unique_index, which happens to be a template itself. Thanks a bunch. --DD