Re: [ ruby-Bugs-3506 ] Set containing duplicates

On 2006.02.09 08:44, Joel VanderWerf wrote:
> Joel VanderWerf wrote:
> > Daniel Berger wrote:
> >> [e-mail] wrote:
> >>> Bugs item #3506, was opened at 2006-02-08 22:52
> >>> You can respond by visiting:
> >>> http://rubyforge.org/tracker/?func=detail&atid=1698&aid=3506&group_id=426
> >>>
> >>> Category: Core
> >>> Group: None
> >>> Status: Open
> >>> Resolution: None
> >>> Priority: 3
> >>> Submitted By: Stefan Rusterholz (rstefan)
> >>> Assigned to: Nobody (None)
> >>> Summary: Set containing duplicates
> >>>
> >>> Initial Comment:
> >>> If an object added to a set becomes modified and added again it will
> >>> be in the set twice.
> >>> A fix to this would be to add "@hash.rehash" in "def add(o)" and "def
> >>> merge(enum)". Though this might minder the speed advantage of set.
> >>> OTOH Set becomes quite useless if it is impossible to add without
> >>> checking first if the element already contained.
> >> I don't see it:
> >>
> >> require "set"
> >>
> >> x = "foo"
> >>
> >> set = Set[x,"bar","baz","foo"]
> >> p set # #<Set: {"baz", "foo", "bar"}>
> >>
> >> set.add("foo")
> >> p set # #<Set: {"baz", "foo", "bar"}>
> >>
> >> x.chomp!
> >> set.add(x)
> >> p set ##<Set: {"baz", "foo", "bar"}>
> >>
> >> Can anyone demonstrate the bug he is referring to?
> >>
> >> - Dan
> > 
> > irb(main):020:0> s = Set[]
> > => #<Set: {}>
> > irb(main):021:0> a = []
> > => []
> > irb(main):022:0> s << a
> > => #<Set: {[]}>
> > irb(main):023:0> a << 3
> > => [3]
> > irb(main):024:0> s << a
> > => #<Set: {[3], [3]}>
> > 
> 
> I don't think it's really a bug. If you have a set with members (like
> Arrays) that hash based on their contents (rather than object id), and
> if you modify those members, then you should rehash. It's the same
> "problem" with Hash:
> 
> irb(main):025:0> h = {}
> => {}
> irb(main):026:0> h[a] = 1
> => 1
> irb(main):027:0> h
> => {[3]=>1}
> irb(main):028:0> a << 4
> => [3, 4]
> irb(main):029:0> h[a] = 2
> => 2
> irb(main):030:0> h
> => {[3, 4]=>2, [3, 4]=>1}

Might it be appropriate to add a similar method to Set, then? 
Call it #reset for some additional humour value.

>       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407


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