Hello,
Item "disappears" in Bag after contents of the item changes. Item is container with equality and hash is overridden. Is this a Bug?
bag:= Bag with: (val := AKContainer value: 'a'). val value: 'b'. bag valuesAndCounts includesKey: val. "false in Trunk,"
set:= Set with: (val := AKContainer value: 'a'). val value: 'b'. set includes: val. "true"
dictionary:= Dictionary newFromPairs: {val := AKContainer value: 'a'. 1}. val value: 'b'. dictionary includesKey: val. "true"
All tests fails in Squeak 3.6 and in Dolphin ST. In Trunk fails only the Bag.
If this is not a bug, how can I escape this Anomaly of disappearing element [1] Thank you Vaidotas
[1] http://books.google.lt/books?id=W8_Une9cbbgC&pg=PA76&lpg=PA76&dq...
On Fri, 30 Jul 2010, Vaidotas Didžbalis wrote:
Hello,
Item "disappears" in Bag after contents of the item changes. Item is container with equality and hash is overridden. Is this a Bug?
No it's not. Since the return value of AKContainer >> #hash and AKContainer >> #= depend on 'value', they will change if you change the 'value'. Hashed collections assume that the hash and equality of the contained objects don't change.
bag:= Bag with: (val := AKContainer value: 'a'). val value: 'b'. bag valuesAndCounts includesKey: val. "false in Trunk,"
set:= Set with: (val := AKContainer value: 'a'). val value: 'b'. set includes: val. "true"
That happens, because String >> #hash doesn't work well with 5: ($a to: $z) collect: [ :each | each asString hash \ 5 ] as: Set "===> a Set(4)" Most of the time it's expected to return false.
dictionary:= Dictionary newFromPairs: {val := AKContainer value: 'a'. 1}. val value: 'b'. dictionary includesKey: val. "true"
Same as above.
All tests fails in Squeak 3.6 and in Dolphin ST. In Trunk fails only the Bag.
So it's just bad luck that these don't fail in Squeak trunk.
Levente
If this is not a bug, how can I escape this Anomaly of disappearing element [1] Thank you Vaidotas
[1] http://books.google.lt/books?id=W8_Une9cbbgC&pg=PA76&lpg=PA76&dq...
So, one needs to remember and rehash some collections manually after mutable object is changed? Brrr. I will forget.
2010/7/30 Levente Uzonyi leves@elte.hu:
On Fri, 30 Jul 2010, Vaidotas Didžbalis wrote:
Hello,
Item "disappears" in Bag after contents of the item changes. Item is container with equality and hash is overridden. Is this a Bug?
No it's not. Since the return value of AKContainer >> #hash and AKContainer
#= depend on 'value', they will change if you change the 'value'. Hashed
collections assume that the hash and equality of the contained objects don't change.
bag:= Bag with: (val := AKContainer value: 'a'). val value: 'b'. bag valuesAndCounts includesKey: val. "false in Trunk,"
set:= Set with: (val := AKContainer value: 'a'). val value: 'b'. set includes: val. "true"
That happens, because String >> #hash doesn't work well with 5: ($a to: $z) collect: [ :each | each asString hash \ 5 ] as: Set "===> a Set(4)" Most of the time it's expected to return false.
dictionary:= Dictionary newFromPairs: {val := AKContainer value: 'a'. 1}. val value: 'b'. dictionary includesKey: val. "true"
Same as above.
All tests fails in Squeak 3.6 and in Dolphin ST. In Trunk fails only the Bag.
So it's just bad luck that these don't fail in Squeak trunk.
Levente
If this is not a bug, how can I escape this Anomaly of disappearing element [1] Thank you Vaidotas
[1]
http://books.google.lt/books?id=W8_Une9cbbgC&pg=PA76&lpg=PA76&dq...
Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
"Vaidotas" == Vaidotas Didžbalis vaidasd@gmail.com writes:
Vaidotas> So, one needs to remember and rehash some collections manually after Vaidotas> mutable object is changed? Brrr. I will forget.
How else would it be?
If its identity-for-equality is based on its contents, how do you expect the collection to reidentify it?
Note that IdentityDictionary doesn't suffer from this.
beginners@lists.squeakfoundation.org
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Levente Uzonyi -
merlyn＠stonehenge.com -
Vaidotas Didžbalis