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From: stanm@thumper.bellcore.com (Stan Moyer)
Newsgroups: comp.lang.c++
Subject: constructor as default argument
Message-ID: <441@salt.bellcore.com>
Date: 12 Jun 91 13:39:31 GMT
Sender: news@salt.bellcore.com
Lines: 39

I am having trouble using a constructor as a default argument for a
function. I am using cfront V2.1 Here is a sample of what I have tried
and the resulting error messages.

class X {
public:
	X(int);
};

const int DEF_X = 0;

class Y {
public:
	Y();
	void f(X x=0);
	void g(X x=X(0));
	void h(X x=DEF_X);
};

functions f & h give me the following error message:
  "sorry, not implemented:  constructor needed for argument initializer"
function g gives me the following error message:
 "sorry, not implemented:  constructor as default argument"

I really didn't expect f to work, but I thought g & h would be valid.

Is this not allowed in C++? Can you only use fundamental data types as
default arguments? Does this not work because a default argument must be
a compile-time constant? I could not find anything about it in the ARM.
Any help would be appreciated.

Thanks in advance,

Stan Moyer

<stanm@thumper.bellcore.com>; Bellcore, MRE-2A219;
445 South Street, Morristown, NJ 07962-1910
voice: +201.829.4923; fax: +201.984.2283