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How to port VW "Signal" to Squeak

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Alejandro Martínez

How to port VW "Signal" to Squeak

Hello. I'm trying to figure out how to port a #newSignal message send from a VisualWorks application (something like Object informationSignal newSignal) to Squeak, which lacks of Signal class. Does anybody know how to do it or have a guideline for this?
Thanks

Alejandro

Andreas.Raab

Re: How to port VW "Signal" to Squeak

Use Squeak exception classes. I don't remember this exactly (it has been
more than ten years since I used it) but it went somewhat along the
lines that "Object informationSignal" would answer the exception class
(Signal in VW?), #newSignal would create an instance and #raise would
raise the signal. Translated to Squeak that means roughly:

VW: (Object informationSignal) newSignal raise
Squeak: (SomeExceptionClass) new signal

Someone please correct me if I remember this wrongly.

Cheers,
- Andreas

Alejandro Martínez wrote:

> Hello. I'm trying to figure out how to port a #newSignal message send
> from a VisualWorks application (something like Object informationSignal
> newSignal) to Squeak, which lacks of Signal class. Does anybody know how
> to do it or have a guideline for this?
> Thanks
>
> Alejandro
>
>
> ------------------------------------------------------------------------
>
>

Alan L. Lovejoy

RE: How to port VW "Signal" to Squeak

In reply to this post by Alejandro Martínez

InformationSignal is simply a subclass of Exception.

The message #newSignal simply answers a new instance of an Exception--typically, an instance of the receiver, which would usually be some subclass of Exception.

The messages and class names result from the fact that Exceptions in VW were originally instance based, not class based. If I remember correctly, it was VisualWorks 1.0 (1990) that introduced Exceptions (instance based) to Smalltalk, not just to the ParcPlace branch of Smalltalk. Personally, I find the instance-based implementation to be more elegant. I strongly dislike any design approach that results in an explosion of different classes, none of which have behavior that significantly differs from that of its cousins. The upside of the class-based approach is simply that it makes file-in/file-out of shared globals so easy. But I see that as a problem with the infrastructure for managing globals, shared pools and namespaces, and not as a good reason to use classes as heavyweight globals.

--Alan

Alejandro Martínez

Re: How to port VW "Signal" to Squeak

In reply to this post by Andreas.Raab

2007/2/21, Andreas Raab <[hidden email]>:

Use Squeak exception classes. I don't remember this exactly (it has been
more than ten years since I used it) but it went somewhat along the
lines that "Object informationSignal" would answer the exception class
(Signal in VW?), #newSignal would create an instance and #raise would
raise the signal. Translated to Squeak that means roughly:

VW: (Object informationSignal) newSignal raise
Squeak: (SomeExceptionClass) new signal

Thanks, that's right, what I'm looking for is the appropiate class equivalent (SomeExceptionClass) in Squeak.

Someone please correct me if I remember this wrongly.

Cheers,
- Andreas

Alejandro Martínez wrote:

> Hello. I'm trying to figure out how to port a #newSignal message send
> from a VisualWorks application (something like Object informationSignal
> newSignal) to Squeak, which lacks of Signal class. Does anybody know how
> to do it or have a guideline for this?
> Thanks
>
> Alejandro
>
>
> ------------------------------------------------------------------------
>
>