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From: hannum@mahler.psu.edu (Charles Hannum)
Newsgroups: comp.lang.c++
Subject: Re: problems with [] operator
Message-ID: <1990Jul6.125741.28182@acc.stolaf.edu>
Date: 6 Jul 90 12:57:41 GMT
References: <27893@ethz-inf.UUCP>
Sender: news@acc.stolaf.edu
Organization: The Pennsylvania State University Public NeXT Laboratory
Lines: 35
In-Reply-To: reberhar@ethz-inf's message of 28 Jun 90 15:07:57 GMT


In article <27893@ethz-inf.UUCP> reberhar@ethz-inf (Rolf Georg Eberhardt) writes:

   ...
   In all C++ books I've looked into the []-operator must return a reference.
   ...


You just answered your own question [B-)].  "Reference to T" and "pointer to T"
are NOT the same.  They are stored the same internally, but "reference to T" is
treated exactly as if it were a "T", whereas "pointer to T" is distinct.

For example, if one declares:

  struct foobar {
    int bar;
  } foo[20];

foo[] returns a foobar, not a foobar*.  To demonstrate:

  foo[10]->bar = 0;		// error: non-pointer -> bar
  (&foo[10])->bar = 0;		// ok (In this case, we're forcing it to treat
				   foo[] as a pointer by using the & operator.)

This is what you really wanted to say before:

  foo[10].bar = 0;

The reader can extrapolate this to the previous case.
--
 
Virtually,
Charles Martin Hannum		 "Those who say a thing cannot be done should
Please send mail to:		  under no circumstances stand in the way of
hannum@schubert.psu.edu		  he who is doing it." - a misquote