Re: [boost] Efficient tuple implementation

Subject: Re: [boost] Efficient tuple implementation
From: Louis Dionne (ldionne.2_at_[hidden])
Date: 2014-06-16 19:55:38

Larry Evans <cppljevans <at> suddenlink.net> writes:

> 
> On 06/15/14 08:44, Louis Dionne wrote:
> > Larry Evans <cppljevans <at> suddenlink.net> writes:
> >
> >>
> >> On 06/06/14 21:18, Louis Dionne wrote:
> >>>
> >>> [...]
> >>>
> >>
> >> IIRC, list uses an evaluator and "tagged" lists where the 1st element in
>           ^^^^ should be lisp
> >> the list is a tag for the operation to be performed and the
> >> evaluator dispatches on this tag to do the operation with the
> >> operands being the remaining args in the list.
> >
> > I don't understand which list you are talking about.
> 
> OOPS.  Very sorry for the typo above.  I'm talking about
> the language, Lisp:
> 
> http://en.wikipedia.org/wiki/Lisp_%28programming_language%29
> 
> and the pattern I was talking about was called "Polish
> prefix notation" in the wikipedia article.

Ok, now I understand better. As for your question, I did not follow the
development of Spirit X3 close enough to know for sure. However, if you
have to store variadic arguments, using a lambda somewhere in there is
probably the most efficient way. And as soon as you have stuff in a
variadic representation, it's better if you keep it that way because
most algorithms will perform better on variadic packs. 

The way I see it for Boost.Hana, your dispatching system could be used 
internally as an optimization to dispatch efficient operations on variadics, 
while keeping the more flexible type class based dispatching interface. I'll
keep that on the back of my head for when I start optimizing seriously.

Thanks,
Louis