[boost] Re: Re: Re: Re: is_convertible: rationale and wording

From: Mike Conley (conley.141_at_[hidden])
Date: 2003-04-27 10:32:49

David Abrahams <dave_at_[hidden]> wrote in 
news:ubrys7jp1.fsf_at_[hidden]:

> That completely scuttles the ODR, as far as I can tell.

Naturally, you wouldn't want to use a built in is_convertible this way.  
Better to pass it as a template parameter directly, rather than wrapping 
it:  and_<is_const<T>, is_convertible<T,int> >.  

If you know that the result of is_convertible depends on context, and you 
know about the ODR, then you know not to use is_convertible to as part of a 
metafunction's return value without also making it part of the 
metafunction's type (ie, using it as a template parameter).

-- 
Mike Conley