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Subject: Re: [boost] [type_at] Variadic template utility
From: Larry Evans (cppljevans_at_[hidden])
Date: 2011-05-26 07:19:50

On 05/26/11 04:47, tymofey wrote:
>> Robert Jones <robertgbjones_at_[hidden]>
>> On Thu, May 26, 2011 at 8:34 AM, tymofey <tymofey_at_[hidden]> wrote:
>>> While experimenting with varidic templates of the upcoming standard i
>>> discovered that quite often one would need to extract a type from parameter
>>> pack at specified position.
>> Forgive me if I'm missing the point, but isn't this essentially Boost.MPL's
>> 'at' metafunction?
>> - Rob.
> It is, but without the need to drag in mpl::vector with the limitations it imposes.
Could you please describe those limitations, other than the one for
maximum arity, which, IIUC, is modifiable by redefining the macro:


? Also, IIUC, one reason for using the macro, and the preprocessor,
is to speed compile time by reducing the number of template
instantiations. Thus, maybe one advantage of mpl::at vs your type_at
is compile time. You might check that somehow.


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