Re: [boost] [fusion] Any chance we can incorporate more folds?

Subject: Re: [boost] [fusion] Any chance we can incorporate more folds?
From: Larry Evans (cppljevans_at_[hidden])
Date: 2010-08-20 23:40:56

On 08/20/10 16:21, Steven Watanabe wrote:
[snip]
>
> We already have reverse_fold, which makes 2/4.
>
fusion::reverse_fold takes the sequence as the first argument.
In contrast, the haskell function takes the sequence as the last
argument.  That wouldn't be a big problem except if you plan to
provide a variadic template:

http://www.osl.iu.edu/~dgregor/cpp/variadic-templates.html

version of these functions.  The variadic template spec
requires the parameter pack to be at the end, IOW:

   template<typename Op, typename State0, typename... Values)
   foldl(Op,State0,Values&... values);

Which is exactly the way haskell orders the arguments.
I know this is different than the way fusion and mpl do it;
however, if arg packs (e.g. Values&... values) are to be used,
then I don't see any workaround.

-Larry