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From: jbuck@galileo.berkeley.edu (Joe Buck)
Newsgroups: comp.lang.c++
Subject: Re: char *const assignment in constructor
Message-ID: <11485@pasteur.Berkeley.EDU>
Date: 27 Feb 91 06:31:17 GMT
References: <1991Feb26.195200.8763@urbana.mcd.mot.com>
Sender: news@pasteur.Berkeley.EDU
Reply-To: jbuck@galileo.berkeley.edu.UUCP (Joe Buck)
Organization: U.C. Berkeley -- ERL
Lines: 33

In article <1991Feb26.195200.8763@urbana.mcd.mot.com> qbarnes@urbana.mcd.mot.com (Quentin Barnes) writes:
>I would like to have a variable of type "char *const" (pointer itself
>is const, not what it points to.)  However, I would like to delay its
>initialization until the contructor is called for its class.  Once it
>is initialized there, I would like the variable treated as const.
>
>Is there any way to do this in C++?

Yes.

class Quentin {
private:
	char *const constPtr;
public:
	Quentin (char *arg) : constPtr(arg) {}
};

This is one of the two cases where you must use the "colon" notation
to initialize members; the other is for reference members.  That is,
writing the constructor

	Quentin (char *arg) { constPtr = arg; }

is illegal.  Why?  Because the language designers tried to make a
distinction between initialization and assignment -- you can initialize
a const object or a reference but you cannot assign to it.



--
--
Joe Buck
jbuck@galileo.berkeley.edu	 {uunet,ucbvax}!galileo.berkeley.edu!jbuck