Begin forwarded message: Date: December 19, 2008 7:52:21 PM CEST Subject: Re: [squeak-dev] Re: Resume Problems
I made sure this was fixed in VisualWorks. Steve Dahl and I fixed this together. Here's an analogous fix for Squeak. The essential change is to make Object>>doesNotUnderstand: check if the MessageNotUnderstood exception was handled or not, so
MessageNotUnderstood new message: aMessage; receiver: self; signal. ^ aMessage sentTo: self.
is replaced with
(exception := MessageNotUnderstood new) message: aMessage; receiver: self. resumeValue := exception signal. ^exception reachedDefaultHandler ifTrue: [aMessage sentTo: self] ifFalse: [resumeValue]
HTH
On Fri, Dec 19, 2008 at 8:13 AM, Zulq Alam <[email protected]> wrote: Hi Klaus, Klaus D. Witzel wrote: Nah, the result has nothing to do with #on:do: resuming with 1, you better
try
[('abc' + 1) + 1]
on: MessageNotUnderstood
do: [:e | e resume: -1]
which still says 2. This because someone, behind you back, put #asNumber
arithmethic into ByteString ... now this attempts (Number readFrom: 'abc')
which gives 0 for your +1 +1 and so 2.
You may want to start DNU testing with ('abc' break; + 1) and then see
where it goes.
Hmm... I think something is not right or at the very least the semantics are subtly different than I expect.
VisualWorks:
[Object new blah + 1]
on: MessageNotUnderstood
do: [:e | e resume: 1] " = 2 "
[MessageNotUnderstood signal + 1]
on: MessageNotUnderstood
do: [:e | e resume: 1] " = 2 "
Squeak:
[Object new blah + 1]
on: MessageNotUnderstood
do: [:e | e resume: 1] " infinite recursion!!! "
[MessageNotUnderstood signal + 1]
on: MessageNotUnderstood
do: [:e | e resume: 1] " = 2 "
If I look at doesNotUnderstand: in both I see that in VW the resumed value is returned. In Squeak is is not... surely this can't be right?
As for my problem, I think a simpler solution is to pass an adaptor/proxy object to the block rather than the tag itself. This adaptor can then marshal behaviour such that it will act as a message eating null if it receives an MNU from the tag it's looking after.
Thanks,
Zulq.
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SqueakMNUaLaVW.1.cs
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