Re: [boost] [proto] transform for flattening an expression - how?

From: Eric Niebler (eric_at_[hidden])
Date: 2008-03-17 18:55:07

Larry Evans wrote:
> Me too!  

I couldn't tell from your email -- what are you me too-ing?

> In general, there should be an n-ary version of all the
> binary ops. 

Do you mean, you'd like to create an expression expr<tag::plus, 
args4<A,B,C,D> > ? There's nothing stopping you from doing that today.

   make_expr<tag::plus>(1,2,3,4)

The only problem is that default_context won't know what to do with it, 
but that's not big a problem ... just write your own context.

> This should also be extended to the or_ also.
> I remember having a problem with folding or_ because it was
> an n-ary op and had to define my own binary or which just
> forwarded to the or_.  That was a "kludge".  So maybe
> define or_ as binary and then define the n-ary version
> based on this binary.

IIRC, your problem was that or_ requires at least 2 parameters. I had 
agreed to change that, but haven't yet.

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com