Question

Calling

std::count_if(vec.begin(), vec.end(), std::bind2nd(std::ptr_fun(foo), 17)) 

works fine with

bool foo(int, int),

but I can’t make it work with

bool foo(const int &, const int &)

Is there a way to make that work or do I have to write my own adaptor function?

Answer 1

The second argument is a number, and cannot be converted to const int &.

You can use boost::bind to do the trick:

std::count_if (vec.begin(), vec.end(), boost::bind (foo, _1, 17));

EDIT:

As of my first response, yes, you cannot use a variable instead of the number. I think the problem is bind2nd and ptr_fun not being properly defined to dereference the type in the case it is a reference when ptr_fun builds the internal Operation object, so ither go with boost or write your own functor class.