Re: [boost] [mpl][fold.html] apply<op, _1, deref<_2> > correction needed.

Subject: Re: [boost] [mpl][fold.html] apply<op, _1, deref<_2> > correction needed.
From: Larry Evans (cppljevans_at_[hidden])
Date: 2009-03-14 07:24:47

On 03/13/09 22:02, Larry Evans wrote:
[snip]
> Has a test showing apply<op,_1,deref<_2> > fails and, in addition
> to the lambda<op>::type::apply<_1,deref<_2> > solution, shows
> another solution which involves changing the apply template
> to *not* inherit from apply_wrap.  Any ideas about which solution
> is better?

OOPS.  The 2nd solution of redefining apply to contain
nested

   typedef apply_wrap<,,> type;

instead of inheriting apply_wrap would obviously break existing code.
However, to get something similar to the apply<op,_1,deref<_2> > in:

   http://www.boost.org/doc/libs/1_38_0/libs/mpl/doc/refmanual/fold.html

to work, maybe using eval_apply (defined as the app2ok in the vault)
would work?  Then instead of:

   apply<op,_1,deref<_2> >

use:

   eval_apply<op,_1,deref<_2> >::type

as shown in the vault code.

The name eval_apply is modeled after eval_if.

Am I missing something or should I file a trac ticket on this?

Note, the ticket woul only say there's a bug in fold.html.
It would say nothing about bugs in fold.hpp.