Re: [boost] [GSoC][MPL11] Post C++Now update

Subject: Re: [boost] [GSoC][MPL11] Post C++Now update
From: Larry Evans (cppljevans_at_[hidden])
Date: 2014-05-20 16:20:31

On 05/20/14 13:59, Larry Evans wrote:
> On 05/18/14 15:41, Louis Dionne wrote:
[snip]
>> Request for guinea pigs
>> -----------------------
>> I am looking for people with hardcore C++1y metaprogramming needs who
>> will
>> be willing to test the library I come up with (MPL11 or MPL + Fusion
>> merge).
>> I also need to see use cases for the library, so please reply even if you
>> are not willing to test.
>>
>
> As mentioned in this post:
>
> https://groups.google.com/forum/?hl=en#!msg/comp.std.c++/_-6X_xZlKlA/-HhvKh5ccEAJ
>
>
> One use case is:
>
>  > 3) A guaranteed non-recursive way to access elements of parameter
>  > packs
>
> and Doug Gregor (quoting from above post) says:
>
>    This is probably the most-requested feature for variadic templates,
>    and it never it made it because we never found a good, unambiguous
>    syntax.
>
> The attached seems to do that.  What about adding something
> like this to the library?
>
> -regards,
> Larry
>
I should clarify something from my previous post.

The at_c.cpp attachment to my previous post *did* use recursion;
however, it was template function recursion, not
template metafunction recursion.

According to:

http://cpptruths.blogspot.com/2011/07/want-speed-use-constexpr-meta.html

template function recursion *should* compile faster than template
metafunction recursion.  Although the above web page uses constexpr,
there's no need for that in the at_c.cpp attachment because only
the types are used, not the values (hence, the functions don't need
to be defined).

Sorry for being unclear.

-regards,
Larry