Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!news.uu.net!taumet!steve
From: steve@taumet.com (Stephen Clamage)
Newsgroups: comp.lang.c++
Subject: Re: Derived/Base Class constructor relationship
Message-ID: <743@taumet.com>
Date: 22 May 91 16:09:28 GMT
References: <29534@hydra.gatech.EDU>
Distribution: na
Organization: Taumetric Corporation, San Diego
Lines: 36

gt5595c@prism.gatech.EDU (BARTZ) writes:

>class A
>{
>   A(int f1,int f2,double first ...); // Constructor of base class
>   ...
>};

>class B : public A
>{
>	B(int g1,double first ...) : Matrix(g1,g1,first) {};
>		 // Constructor for derived class
>	...
>};

>The constructor for the base class works OK with the ellipse 
>but the derived class construction does not work.  The base class
>constructor is not called with the list of doubles.

I assume you meant
	B(int g1, double first ...) : A(g1, g1, first) {};

There is no syntax to support passing along a variable parameter list
this way.  Two solutions come immediately to mind:

1.  Don't use variable parameter lists for the B constructor.  Use an
    array of doubles and a count, for example, and add an A
    constructor which does the same:
	B::B(int g1, double *aray, int count) : A(g1, g1, aray, count) {}

2.  Make A a member of B instead of deriving B from A.  Then A can have
    an additional constructor taking a va_list parameter, and the B
    constructor can set up the va_list and invoke the A constructor.
-- 

Steve Clamage, TauMetric Corp, steve@taumet.com