Xref: utzoo comp.lang.c++:13286 comp.std.c++:892
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!wuarchive!uunet!taumet!steve
From: steve@taumet.com (Stephen Clamage)
Newsgroups: comp.lang.c++,comp.std.c++
Subject: Re: Default type of "0"
Message-ID: <713@taumet.com>
Date: 7 May 91 15:18:08 GMT
References: <74609@brunix.UUCP>
Followup-To: comp.lang.c++
Organization: Taumetric Corporation, San Diego
Lines: 25

sdm@cs.brown.edu (Scott Meyers) writes:

>What is the type of the constant "0", independent of any context?

A literal zero has type int.  It can also serve as a null pointer constant
when initializing a pointer.

	int i = 0;	// 0 has type int
	double d = 0;	// 0 implicitly converted to type double
	T* t = 0;	// 0 implicitly converted to type T*
	T* u = i;	// illegal, since i is not a null pointer constant

>The reason for asking is that it would be nice to avoid the following
>ambiguity:

>    void f(int x);     // parameter of a numerical type
>    void f(char *s);   // parameter of a pointer type
>    f(0);              // ambiguous call -- is 0 an int or a char*?

This is not ambiguous.  The zero is an exact match to f(int), but
requires a conversion to f(char*).  If your compiler calls it ambiguous,
this is a bug.
-- 

Steve Clamage, TauMetric Corp, steve@taumet.com