It's really strange, these two works in my image (Squeak-3.9-7058):

(Set withAll: #(a b c a) ) removeAllSuchThat: [:x | x == #a ].
(OrderedCollection withAll: #(a b c a) )
      removeAllSuchThat: [:x | x == #a ].

May be you can get the same effect with something like this:
(the worst case it's O(n^2) like removeAllSuchThat: in Collection)

| s |
s := Set withAll: #(a b c a).
s removeAll: (s select: [:x | x == #a ]).

It's really necesary to keep the same Collection instance (why not
simply reject:) ?

On 9/19/06, Leandro Caniglia <caniglia at dm.uba.ar> wrote:
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> What's the best way to implement the method of the subject?
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> self removeAllSuchThat: [:x | x == anObject] won't work.
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> /Leandro
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