Re: [boost] Do-nothing binary function

From: Brian McNamara (lorgon_at_[hidden])
Date: 2003-08-29 23:09:37

On Thu, Aug 28, 2003 at 03:59:19PM +0400, Vladimir Prus wrote:
> 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 {}
> 
>        //....
> }

Someone has already commented WRT bind/lambda.  Just FYI (as more
support that, yes, it can be generally useful), in FC++

   no_op

is the (nullary) do-nothing function object, and thus

   ignore(ignore(no_op))

is the function you've written above.  (ignore() is a combinator which
takes a function and returns a new function which takes an extra first
argument and ignores it.)

> 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.

Again, I imagine you do something similar with bind/lambda; in FC++:

   ignore(ignore(const_(true)))
or
   lambda(X,Y)[ true ]

-- 
-Brian McNamara (lorgon_at_[hidden])