On Fri, Jul 17, 2009 at 2:22 PM, Ralph Boland <rpboland at gmail.com> wrote:

> In my own Squeak project I have a method
>
> Dictionary>>rehash.
>
> I don't remember why I wrote this method but
> I just noticed that Dictionary>>rehash is not in
> the original  Squeak 3.10.2 code.
> Furthermore if used it should fail because
> it will inherit rehash from Set which doesn't
> work for Dictionaries.  My Dictionary>>rehash
> method is like the one in Set except
> associationsDo:  is used instead of  do:.
>
> Is this a bug?


Which, the absence of the method, the default to Set>>hash or the use of
associationsDo: ?
yes. yes. no.

Note that in our system we have

Dictionary methods for private
rehash
"Smalltalk rehash."
| newSelf |
newSelf := self species new: self size.
self associationsDo: [:each | newSelf noCheckAdd: each].
array := newSelf array

What is the purpose of rehash anyway?


Rehash arranges that a hashed collection's contents are again accessible
after hashes have changed.  For example, if one changes the hash method(s)
of classes of elements of hashed collections one would need to rehash
afterwards to keep those collections working properly.  One common uses is
on loading objects from some binary stream where the newly created loaded
objects have different hashes than they had when they were saved, and hence
hashed collections referring to those objects must be rehashed sometime
during the load process.

So that the Dictionary>>rehash method is missing is a bug, and that you're
doing the right thing is not.

HTH


>
> Ralph Boland
>
>
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