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From: bmc@mayo.edu (Bruce Cameron)
Newsgroups: comp.lang.c++
Subject: Accessing base class constructors
Message-ID: <1991Jun12.183837.15084@bmw.mayo.edu>
Date: 12 Jun 91 18:38:37 GMT
Sender: newsman@bmw.mayo.edu (USENET News manager)
Organization: Biomedical Imaging Resource
Lines: 128

Being a novice to C++, I do not understand why I am unable to access a
base class' constructor from a derived class. I understand the syntax
to be:

	dc::dc(dc ctor params):[bc](bc ctor params)
	{
	body of dc ctor
	}

Yet when I try to do this with a base class that makes use of a vararg
list I get a variety of syntax errors (using Sun C++2.1). Is it
possible to have a base class constructor with a vararg list and
derive classes from it that initialize the base class through its
constructor? If not, any work arrounds for this? How are these
supposed to work?

Thanks for any and all help.

(only error I get is line 57: syntax error)

Sample code I'm trying:

#include <stdlib.h>
#include <stream.h>
#include <stdarg.h>

class base {
	private:
		int	*b1;

	protected:
		int	b2, b3;

	public:
		base (int a ...);
		void bar ();
};

class derived : public base {
	private:
		int	*d1;

	protected:
		base::b2;
		base::b3;
		int	d2;

	public:
		derived (int a, int *b, int c ...);
		void foo ();
};

base::base (int a ...)
{
	va_list		va;

	b2 = 3;
	b3 = 2;
	b1 = new int[b2];
	for (int i = 0; i < b2; i++) b1[i] = b3;

	va_start (va, a);
	if (!(a)) return;
	if (!(b3 = va_arg (va, int))) return;

	b2 = a;
	delete b1;
	b1 = new int [b2];
	for (i = 0; i < b2; i++) b1[i] = b3;
}

void base::bar ()
{
	for (int i = 0; i < b2; i++)
		cout << b1[i] << " ";
}


derived::derived (int a, int b):(int c ...)
{
	d2 = a;
	d1 = new int [d2];
	for (int i = 0; i < d2; i++) d1[i] = b;
}

void derived::foo()
{
	if (d2 < b2) {
		for (int i = 0; i < d2; i++) 
			if (d1[i] < b3) d1[i] = b3;
		}
	else {
		for (int i = 0; i < b2; i++)
			if (d1[i] > b3) d1[i] = b3;
		}
	for (int i = 0; i < d2; i++)
		cout << d1[i] << " ";
}

main ()
{
	base	b (6,12);
	derived	d (12,6);

	cout << "base class\n";
	b.bar();
	cout << "\n derived class \n";
	d.foo();
}


-- 
--Bruce

"An eye for an eye makes the whole world blind"
				Ghandi
----------------------------------------------------
Bruce M. Cameron                    bmc@bru.mayo.edu
Medical Sciences 1-14               voice: (507) 284-3288
Mayo Foundation                     fax:   (507) 284-9623
200 1st ST SW				
Rochester, MN 55905		    ARS -- WD9CKW
----------------------------------------------------
The views expressed are those of the author and do not reflect
those of the Mayo Foundation, the Biomedical Imaging Resource
or any person connected with those organizations.

They don't speak for me, I don't speak for them.