[Boost-users] [Bind] How to create a functor which returns one of its arguments?

Subject: [Boost-users] [Bind] How to create a functor which returns one of its arguments?
From: Vadim Guchenko (nomail_at_[hidden])
Date: 2009-12-08 08:05:26

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; }
};

Then I could write:

boost::bind(arg<int>(), _2)

to create a functor which returns the value of its second argument, or

boost::bind(arg<bool>(), true)

to create a functor which always returns true.

--
Best regards, Vadim Guchenko [yhw at relost dot net].