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

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 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.)