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From: bs@alice.UucP (Bjarne Stroustrup)
Newsgroups: net.lang.c++
Subject: cfront working too hard?
Message-ID: <5018@alice.uUCp>
Date: Sat, 22-Feb-86 08:57:23 EST
Article-I.D.: alice.5018
Posted: Sat Feb 22 08:57:23 1986
Date-Received: Mon, 24-Feb-86 08:31:26 EST
Organization: Bell Labs, Murray Hill
Lines: 48

> From: mat@mtx5a.UUCP (m.terribile)
> Newsgroups: net.lang.c++
> Subject: cfront working too hard?
> Organization: AT&T Information Systems, Middletown, NJ 07748-4801.
>
> In compiling a base class b with virtual function v, I declare
>  
>	virtual int
>	b::v( b* bp )
>	{
>		return 0;
>	}
>
> where the intent is that derived classes may have good use for bp, but
> the base class represents a null case.
>
> cfront naturally warns about the unused argument.
>
>	Is this excessive in the case of a virtual function?  Is there
> a syntax (such as omitting ``bp'') that will allow me to say ``I know
> that an argument is passed, but I don't need it'' ?  With virtuals, this
> might be a common situation.

You need not give an argument a name if you don't use it:

	virtual int b::v(b*)
	{
		return 0;
	}

This is occationally also useful for non-virtual functions. The typical reason
is that an argument is not yet used but is a part some agreed upon interface.
It can also happen the other way: an argument used to be needed, but then you
find a way of doing without it. Leaving the argument unused and unnamed rather
than removing it leaves the ``official'' interface unchanged.

>	As usual, if this could better have been handled by private mail,
> sill someone please let me know?

As I see it, there are so many people that are new to C++ that most sensible
questions deserve an answer on the net: If you had a problem, someone else
very likely had it too.

>
>	from Mole End			Mark Terribile
>		(scrape .. dig )	mtx5b!mat

	- Bjarne Stroustrup (AT&T Bell Labs, Murray Hill)