Re: Set and .equals() semantics

From:

Tom Anderson <twic@urchin.earth.li>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 9 May 2008 18:21:42 +0100

Message-ID:

<Pine.LNX.4.64.0805091819550.19671@urchin.earth.li>

On Fri, 9 May 2008, Lew wrote:

Tom Anderson wrote:

On the gripping hand, though, how many Sets are actually implemented like
this? Would it be so awful to have a find method in the interface, and
throw a NotImplementedException in the cases where it's impossible?

Thus having a wart function in the interface that is mostly never needed
and might not work in the rare cases where it is.

Cases where it wouldn't work would be even rarer than cases where it was
needed!

So instead of finding a simpler algorithm that doesn't rely on dual
definitions of equality, or using the kindergarten-easy Map<T, T>
solution that everyone else, including HashSet itself, uses, you suggest
that the very Set interface must change

Yup!

for this extremely rare use case that is almost always the product of
incorrect engineering in the application space?

Big words. Evidence for them, please. I won't dispute the rarity, but i'd
like to see your evidence for saying it's almost always the product of
incorrect engineering.

tom

--
.... but when you spin it it looks like a dancing foetus!