Re: [Boost-users] [BGL] property tag classes and "num"

From: Jens Müller (jens.mueller_at_[hidden])
Date: 2006-05-29 14:42:22

Daniel Mitchell schrieb:
> On Monday 29 May 2006 05:20, Jens Müller wrote:
> 
>>Am I missing something, or where is "num"?
> 
> 
> No, you're not missing anything. I think that part of the documentation is a 
> relic from an older version of BGL. If you look in graph/properties.hpp, the 
> property tags are defined like
> 
> namespace boost {
>   enum edge_weight_t { edge_weight };
>   
>   template<>
>   struct property_kind<edge_weight_t> {
>     typedef edge_property_tag type;
>   };
> }
> 
> As you can see, there's no reference to "num." 

OK ...

I used something like I quoted from the docs (struct with only a type),
and then used a default-constructed value (my_property_t()) to access
the map.

Is that "worse style" than the one currently employed in the lib?

Is constructing/passing a struct with no data members more efficient
than it is with an enum, or is there no difference?