[boost] Re: mpl::equal_to changes

From: David Abrahams (dave_at_[hidden])
Date: 2004-09-24 14:37:49

Cromwell Enage <sponage_at_[hidden]> writes:

> --- Ian McCulloch <ianmcc_at_[hidden]>
> wrote:
>> Hi,
>
> Hello.
>
>> Is the following program supposed to compile with
>> the new MPL?
>
> Probably not.
>
>> But, maybe I was mis-using equal_to ?
>
> equal_to<...> no longer accepts bool_<...> or any
> expressions resulting in bool_<...> as a template
> argument, since bool_<...> does not contain a typedef
> named tag (for numeric_cast<...>).  I don't have the
> MPL book, so I don't know the rationale behind it

Unfortunately, that bit isn't covered in the book.  I think Aleksey
added the tag stuff very recently as a way of handling non-integral
numeric types.  It seems to me that bool_ really ought to have
whatever tags int_ has.

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com