From: "David A. Black" Date: 2005-12-06T12:36:21+09:00 Subject: Re: Subclassing Class. Hi -- On Tue, 6 Dec 2005, John Carter wrote: > On Tue, 6 Dec 2005, David A. Black wrote: > > > On Tue, 6 Dec 2005, Aredridel wrote: > > > >> Each Class (and indeed, every other object) has its own private class, > >> for just that object alone, the eigenclass. It can have methods added to > > ^^^^^^^^^^ > > > > Is there any chance of stemming the tide of nicknames and coined synonyms > > for singleton classes? > > Hmm. It's perfectly standard mathematical terminology for an operator A, > if you can find a limited subset of items e_i such that A operating on > item e_i results in the same item e_i (upto a scalar factor), then > the e_i are called an eigenstate of the operator A and the scalar factor > is the eigenvalue. > > This usage of the term "eigen" is far far wider than ruby and far far > older. So are thousands of other usages of "eigen" :-) But I'm not arguing for or against 'eigenclass'. I'm just suggesting that we not enter an era -- or, rather that we leave the era we appear to have entered -- of using a variety of unofficial names for singleton classes as if they were the official name. > > If this usage maps in some fairly clear manner onto singleton classes then > clearly the term singleton class should be dropped in favour of > eigenclass. > > The question then is "Is there an operation which leaves the singleton > classes, and only the singleton classes, unaltered (except perhaps in some > trivial fashion)?" "Eigen" is actually a much more common and adaptable term than that. It's basically German for "own", and appears all over the place in compounds and as a prefix (Eigentum is property (stuff you own), Eigenschaft is a property (in the sense of a characteristic), etc.). No particular antecedent coinage has a claim on Ruby's loyalty. If it's a good replacement for "singleton class", it's because of what "eigen" + "class" suggests in its own right. David __ David A. Black dblack@wobblini.net "Ruby for Rails", forthcoming from Manning Publications, April 2006!