Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!ateng!chip
From: chip@ateng.com (Chip Salzenberg)
Newsgroups: comp.lang.c++
Subject: Re: inheriting an object with a strange constructor...
Message-ID: <25854A95.1251@ateng.com>
Date: 12 Dec 89 18:59:32 GMT
References: <ANDERSNB.89Dec11091454@lab.nyu.edu>
Organization: A T Engineering, Tampa, FL
Lines: 67

According to andersnb@lab.nyu.edu (Brian Anderson):
>class A {
>private:
>	char* thing;	
>public:
>       A(int i...) {
>         // parse arguments
>	}
>};
>
>class B: A {
>public:
>       B(int i...): A(i...) {
>	   // other stuff
>	}
>};

I don't think you can do what I think you want.  But if you provide a version
of A's constructur that's fast and does nothing, you can then call A::init()
with a va_list argument:

	class A {
	public:
		A(int i ...);
	protected:
		init(int, va_list);     // does all the construction work
	private:
		char *thing;
	};

	class B: public A {
	public:
		B(int i ...);
	};

	A::init(int i, va_list ap)
	{
	    if (i)
	    {
		// allocate thing, etc.
	    }
	    else
		thing = NULL;
	}

	A::A(int i ...)
	{
	    va_list ap;
	    va_start(ap, i);
	    init(i, ap);
	    va_end(ap);
	}

	B::B(int i ...)
	  : A(0)  // note that init(0) does nothing important
	{
	    va_list ap;
	    va_start(ap, i);
	    init(i, ap);
	    va_end(ap);
	}

It could get more complicated, but this will work.
-- 
You may redistribute this article only to those who may freely do likewise.
Chip Salzenberg at A T Engineering;  <chip@ateng.com> or <uunet!ateng!chip>
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