Re: [boost] typedefs within Concept or as Trait?

From: Tobias Schwinger (tschwinger_at_[hidden])
Date: 2008-01-11 06:25:10

Doug Gregor wrote:
> On Jan 10, 2008, at 3:40 PM, Michael Fawcett wrote:
>> My questions are - when creating your own library, when do you choose
>> nested typedefs over a traits class,
> 
> Never.
> 
>> and what effects does it have on
>> a library user, both from a usability and extensibility point of view.
>> What questions do you ask yourself to come to a decision?
> 
> 
> Traits classes are far better than nested typedefs, because one can  
> always specialize a traits class for an existing type---even if you  
> can't modify the type because it is built-in or comes from another  
> library that you can't modify.
> 

Type members are inherited by derived classes -- traits specializations 
are not. So I don't think it's generally true that either one is better 
than the other -- it depends on what you're trying to achieve.

Regards,
Tobias