Re: [Boost-users] [Bind] How to create a functor which returns one ofits arguments?

Subject: Re: [Boost-users] [Bind] How to create a functor which returns one ofits arguments?
From: Andrew Maclean (andrew.amaclean_at_[hidden])
Date: 2009-12-08 20:16:36

Why would you do this?
(I mean the  standard unary functor).

Thanks
   Andrew

On Wed, Dec 9, 2009 at 11:10 AM, Peter Dimov <pdimov_at_[hidden]> wrote:
> Vadim Guchenko wrote:
>>
>> Hello, All!
>>
>> Is there a simple way to create a functor that returns one of its
>> arguments _1, _2, ...?
>> Does standard unary functor exist, which simply returns its argument
>> unchanged? I.e.:
>>
>> template<typename T>
>> struct arg: public std::unary_function<T, T> {
>>       T operator()(const T &x) const { return x; }
>> };
>
> It's not part of the current standard, but many implementations provide
> std::identity as an extension. (It will be standard in C++0x.)
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Andrew J. P. Maclean
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