RE: [boost] Proposed metaprogramming type system

From: Geurt Vos (G.Vos_at_[hidden])
Date: 2001-12-17 10:28:42

> > > 
> > > struct missing; // missing argument in a variadic function
> > > 
> > 
> > ...I usually don't like it when something is missing...
> > 
> > IOW, the argument is IMO not missing, it's simply not
> > used, hence I'd say call the thing 'unused' instead...
> 
> An example of an unused argument:
> 
> void f(int)
> {
> }
> 

This is unused from an implementation point of view.
What is unused from an interface point of view?

> An example of a missing argument:
> 
> f();
> 

Hmm, as I see it, missing implies something
was there in the first place. Missing implies
incomplete. 

If f(); is an example of a missing argument, I'd 
expect a compile error (missing argument: 1
expected, 0 found).

When calling f() with no arguments, the argument
isn't missing, it's simply not there - it doesn't exist.

There could of course be a default argument:

    void f(T i = missing);

vs. 

    void f(T i = unused);

Now which one would raise more questions?

Geurt