Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!mailrus!tut.cis.ohio-state.edu!bloom-beacon!gatech!ulysses!hector!jss
From: jss@hector.UUCP (Jerry Schwarz)
Newsgroups: comp.lang.c++
Subject: Re: overloading array indexing
Keywords: [] bugs? array indexing
Message-ID: <10289@ulysses.homer.nj.att.com>
Date: 15 May 88 16:09:03 GMT
References: <451@ethz.UUCP>
Sender: netnews@ulysses.homer.nj.att.com
Reply-To: jss@hector (Jerry Schwarz)
Organization: AT&T Bell Labs, Murray Hill
Lines: 34

In article <451@ethz.UUCP> peter@ethz.UUCP writes:
>
>I have been trying to overload the array indexing operation as part of
>a simulator I am writing. I am getting nowhere fast. 
>
>

The problem is that in the example subsrcipts a tiny*, rather than a
tiny.  Subscripting of pointers in C++ has the builtin meaning and
never invokes a defined operator. The operator[] member is used when
a value of the class type is subscripted.

 class tiny{
     int v;
 public:
     tiny() {v=0;}
     void operator[](int i) { ... }
	// Used when subscripting a "tiny"
 };

 main() {
     tiny    fred[5];
	// array of 5 tiny's
	
     fred[2];
	// equivalent to *(&fred[0]+2), whose evaluation requires
	// no code.

     fred[2][99] ;
        // calls fred's subsrcipting operator, with this==&fred[2].
 }


Jerry Schwarz
Bell Labs, Murray Hill