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Subject: Re: [boost] [type_at] Variadic template utility
From: tymofey (tymofey_at_[hidden])
Date: 2011-05-26 05:47:28


>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. While the task is trivial it would be quite > > handy to have a ready tool for this purpose, rather that specifying one > > yourself every time. > > > > You can find source code consisting of a single header at > > Vault/Utilities/type_at.hpp > > > > The usage is simple: > > > > boost::type_at<index, some_type_0, some_type_1, some_type_2, > > some_type_n>::type > > > > corresponds to some_type_index where index is in range [0..n]. For example: > > > > boost::type_at<2, int, float, char, long>::type > > > > corresponds to char. > > > > > 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.


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