Re: [Boost-users] analogy to mem_fun_ref to member variables

From: Doug Gregor (dgregor_at_[hidden])
Date: 2005-01-27 09:50:10

On Jan 26, 2005, at 7:21 PM, Chris Goller wrote:

> I have a struct that contains two values.
>
> struct box
> {
>    double width;
>    double length;
> }
>
> vector<box> boxes;
>
> I want to accumlate all the widths of the boxes.  The only solution 
> I've found is to create a member function get_width that
> will return the width for use in mem_fun_ref
>
> eg:
>
> accumulate(make_transform_iterator(boxes.begin(), 
> mem_fun_ref(&boxes::get_width)),
> make_transform_iterator(boxes.end(), mem_fun_ref(&boxes::get_width)),
> 0.0,
> plus<double>()));
>
> Is there a boost way of not using mem_fun_ref, but rather returns the 
> public member variable.  Something that could
> be named mem_var_ref that would look like this:
>
> accumulate(make_transform_iterator(boxes.begin(), 
> mem_var_ref(&boxes::width)),
> make_transform_iterator(boxes.end(), mem_fun_ref(&boxes::width)),
> 0.0,
> plus<double>()));
>
>
> This way I wouldn't need to add extra get logic to a structure that 
> doesn't really need it othewise.

You can use boost::mem_fn(&boxes::width).

        Doug