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From: daniel@saturn.ucsc.edu (Daniel Edelson)
Newsgroups: comp.lang.c++
Subject: Re: operator[][]?
Message-ID: <7512@saturn.ucsc.edu>
Date: 16 May 89 20:08:03 GMT
References: <NEATH.89May15154230@solar-1.stars.flab.Fujitsu.JUNET>
Reply-To: daniel@saturn.ucsc.edu (Daniel Edelson)
Distribution: comp.lang.c++
Organization: University of California, Santa Cruz
Lines: 44

In article <NEATH.89May15154230@solar-1.stars.flab.Fujitsu.JUNET> neath@solar-1.stars.flab.Fujitsu.JUNET writes:

>I am trying to determine what support there is in C++ for multi-dimensional
>arrays within a class. For example, the following class definition attempts to
>implement an array of pointers to vectors. Now, I know that I can overload
>operator[], but what I would really like to be able to do is overload the
>ficticious operator[][]. How can I achieve this functionality? Am I missing
>something very obvious?

>Martin Neath <neath@dsg.ti.com>

You need the type of A to be different from the type of A[i]
so that the [] operator applied to expressions of each type 
works correctly. 

Example: 

	class Element { /* stuff */ };

	class Vector {
	private:
		Element * col;		// an array of elements
		...
	public:
		Element & operator[](int index2);
		...
	};

	class Array{
	private:
		Vector * rows;		// an array of vectors
		...
	public:
		Vector & operator[](int index1);
		...
	};

Let A be of type Array, A[i] is of type Vector and
A[i][j] is of type Element. The two instances of the 
subscripting operator in the expression A[i][j] are not 
the same implementation, but are both [] operators.

daniel edelson
daniel@saturn.ucsc.edu