Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uwm.edu!gem.mps.ohio-state.edu!usc!ucla-cs!rutgers!att!dptg!ulysses!andante!alice!ark
From: ark@alice.UUCP (Andrew Koenig)
Newsgroups: comp.lang.c++
Subject: Re: Lvalue checking for operator= ??
Message-ID: <10047@alice.UUCP>
Date: 24 Oct 89 06:24:43 GMT
References: <33433@cornell.UUCP> <10045@alice.UUCP> <874@mit-amt.MEDIA.MIT.EDU>
Organization: AT&T Bell Laboratories, Liberty Corner NJ
Lines: 45

In article <874@mit-amt.MEDIA.MIT.EDU>, peter@mit-amt.MEDIA.MIT.EDU (Peter Schroeder) writes:

> How do I tell the compiler that `*this'
> is const with respect to some operation?

> After all that is really what I need in the above case?!

You put `const' in the appropriate place in the member
function declaration.  For example:

	class Foo {
	public:
		int getsize() const;
		void setsize(int);
		// ...
	};

	int Foo::getsize() const
	{
		int x;
		// ...
		return x;
	}

	void Foo::setsize(int x)
	{
		// ...
	}

Here, the instances of `const' in Foo::getsize() say that
*this is a const inside getsize but not in setsize.  Thus:

	main()
	{
		Foo f;
		const Foo cf;

		f.setsize(3);			// OK
		int n = f.getsize();		// OK
		n = cf.getsize();		// OK
		cf.setsize(7);			// error -- cf is const
	}
-- 
				--Andrew Koenig
				  ark@europa.att.com