Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uwm.edu!ogicse!ucsd!ucbvax!hplabs!hpl-opus!hpnmdla!hpmwtd!jeffa
From: jeffa@hpmwtd.HP.COM (Jeff Aguilera)
Newsgroups: comp.lang.c++
Subject: Re: operator []: ref vs value
Message-ID: <1520022@hpmwjaa.HP.COM>
Date: 23 Feb 90 18:39:28 GMT
References: <5216@brazos.Rice.edu>
Organization: HP Microwave Tech. - Santa Rosa, Ca.
Lines: 17

> I can't seem to find a way to do precisely what I want; I want a
> sparse vector data type.  I can declare a float-returning operator []
> that returns 0.0 if the array index corresponds to a row for which no
> nonzero is stored.  I can declare a reference-to-float-returning
> operator[] that creates a new entry in my linked list of nonzero
> values when the row has no corresponding nonzero stored.
> Unfortunately, I want one behavior when the pseudo-array access occurs
> as an rvalue and another when it appears as an lvalue.  Can I get what
> I want?

Here's one way, but it's not so pretty:  

	float spare_matrix::operator[](int);	//read-only access
	float& spare_matrix::operator()(int);	//possible write-to access

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jeffa