[boost] Do-nothing binary function

From: Vladimir Prus (ghost_at_[hidden])
Date: 2003-08-28 06:59:19

Hi,
just now I've nearly comitted the following addition to one of BGL headers:

+  struct null_property_copier {
+    template<class V1, class V2>
+    void operator()(const V1&, const V2&) const {}
+  };
+

What stopped me is that is not BGL specific at all. Is there some class in 
Boost which can be used insteead? Another BGL header has a class which two 
empty operator() -- one taking single argument, and another taking two 
argument. And that duplication is not good.

Would it be desirabe to have such class? I'm thinking about 

struct do_nothing {
        template<class T>
        void operator()(const T&) const {}

        template<class T1, class T2>
       void operator()(const T1& t1, const T2& t2) const {}

       //....
}

And another question. Do we have a functional object which always returns 
true, and can be called with two arguments of any types? Again, some BGL 
header has such a class in detail namespace.

- Volodya