Re: [Boost-users] [mpl] Implementing eraseVal

30 Mar 2007


      on Thu Mar 29 2007, Scott Meyers  wrote:
...
David Abrahams wrote:
...
Yeah, why struggle?  This problem looks tailor-made for filter_view.
Skipping over the struggling comment (it's not like I'm deliberately choosing 
it),
Sorry.
...
what makes filter_view a better choice?  With both implementations, doesn't 
eraseVal::type yield a new sequence?
I didn't look too closely at what

  template
  struct eraseVal
     : mpl::eval_if<
         boost::is_same::type,
                        typename mpl::end<Seq>::type>,
         typename mpl::identity<Seq>::type,
         eraseVal::type,
                    typename mpl::next::type>::type
                    >::type,
                  T>
       >
  {};

was doing, but it seemed like a much bigger struggle than

  template
  struct eraseVal
    : filter_view > >
  {};
...
If filter_view is always better than copy_if,
why do we need both?
Oh, I didn't see copy_if anywhere.  I'm not sure filter_view is always
better, but the question of why we need both has definitely crossed my
mind, and I don't have a good answer.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com

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