[boost] Re: best way to make {reverse_}fold a sequence

From: Larry Evans (cppljevans_at_[hidden])
Date: 2005-02-28 02:06:46

On 02/28/2005 01:56 AM, David Abrahams wrote:

>> types).  fold and reverse_fold don't even have to _return_ sequences.

Which is what I'm trying to remedy.  I need this because I would like
to use for_each on the result of a fold invokation.

> 
> I can't understand why you're not using Fusion, or at least trying to
> fit into the Fusion framework

Maybe the visitor.hpp in sand-box vault will illustrate.  I found it
convenient to define field_sets, and then make it the base class of
visits_fields<VisitorId> for VisitorId in visitor_numerals (an
enumeration).  IIUC, fusion tuples, if it's like the existing
boost tuple, takes a sequence of types and produces a type; yet,
that wouldn't make field_sets the base type.  I need something
where the base type (corresponding to the default empty_base for
inherit_linearly), is user-specified, and tuples doesn't work.