Re: [boost] Policy or Trait?

From: Rob Stewart (stewart_at_[hidden])
Date: 2004-04-02 10:52:18

From: "Rozental, Gennadiy" <gennadiy.rozental_at_[hidden]>
> 
> > Trait - A class template parameterized on a single type that 
> > associates information with that type.  A traits class, 
> > therefore, provides an external, named grouping of 
> > metainformation, behavior, or both for that type.  A trait 
> > class is never passed as a template parameter; it's name is 
> > ubiquitous. A traits class never has state.
> 
> By state you mean non-static data members, yes?

Yes.

> > Policy - A class template passed to other templates for the 
> > purpose of providing a named grouping of metainformation, 
> > behavior, or both to those templates.  Because it is a 
> > template parameter, different policy classes can be used as 
> > desired.  In many cases, a policy class is used as a base class.
> 
> Well, apparently there is somebody who think the same as I do. 
> 
> Thank you Rob, for your definitions. They seems sound and close to what I
> have in mind.

I'm hoping we can all come to agree on something that usefully
distinguishes these terms.  It is a hindrance to communication if
everyone brings a different interpretation of the words to a
conversation and if the two are thought to be completely
interchangeable, then why use both?

-- 
Rob Stewart                           stewart_at_[hidden]
Software Engineer                     http://www.sig.com
Susquehanna International Group, LLP  using std::disclaimer;