Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!rutgers!att!cbnewsl!dog
From: dog@cbnewsl.ATT.COM (edward.n.schiebel)
Newsgroups: comp.lang.c++
Subject: Re: const and caching
Message-ID: <3053@cbnewsl.ATT.COM>
Date: 28 Nov 89 20:15:05 GMT
References: <4289@cadillac.CAD.MCC.COM>
Organization: AT&T Bell Laboratories
Lines: 26

From article <4289@cadillac.CAD.MCC.COM>, by vaughan@puma.cad.mcc.com (Paul Vaughan):
> 
> 	Consider the method A::foo(), where foo() conceptually does
> not change any aspect of the A object, but does cause some information
> to be cached, so that the next time A::foo() is called, it will return
> (the same result) sooner. 

I have the same problem with const.  I view it as "constant from the
outside" while the language (currently ? :-) considers it as
"constant through and through and no data may change". The way I have
gotten around it is to cast away constness on this. e.g.:

void A::foo() const
{
	// change some cached value
	(foo*)this->cached_value = new_value;
}

This works as long as the compiler didn't decide to put your A into
some deluxe read only memory, in which case the results are
undefined.  For my money, I think this is a reasonable compromise.

	Ed Schiebel
	AT&T Bell Laboratories
	dog@vilya.att.com