2010/4/21 Peter Hugosson-Miller <[email protected]>:
> Hi all,
> So it's time for me to stop lurking and do some stuff. However, although I
> am an experienced Smalltalk programmer (VisualAge Smalltalk continuously
> since 1995), I am a complete newb when it comes to Pharo and Squeak, it's
> hard to find my way around, and it's going to take me some time to get up to
> speed.
> I'm working on a small improvement to the testing framework, using ideas
> that I have found to be very useful in my daily job over the past 15 years.
> Note that I am doing this from scratch, so that I don't accidentally steal
> anything that I've done in my work, but I know how it all works in
> VisualAge, so I feel sure that I'll eventually be able to find the
> corresponding classes and methods in Pharo.
> What I would like are a few hints, clues and nudges in the right direction
> for scenarios and questions that I will describe in this thread. What I
> *don't* want are full-blown solutions, because then I won't learn anything.
> I hope that some kind souls will be able to give me a little help in the
> beginning that will eventually bring me up to speed and let me be
> productive.
> So to start with, one scenario and one question:
> 1) I want to find or write a method on Process that will print a stack trace
> onto a supplied Stream. Ideally I'd like to be able to decide the start and
> stop depth of the trace, so for example if I know that the top 4 stack
> frames will always be uninteresting, I would want to be able to write
> something like this:
> Processor activeProcess printStackFrom: 5 to: 15 on: aStream.
> 2) What *exactly* is "thisContext"? It appears to be a reserved word in
> Pharo, just like the familiar "self", "super", "true", "false", "nil" that
> are always reserved in Smalltalk. I'd also like to get an idea of what it's
> good for, and if anyone can describe it in terms of something that is in
> VisualAge, that would be nice too :-)
thisContext is a special object for representing an activation in a
stack frame in a stack-based VM. There are two kinds of contexts:
Method Contexts and Block Contexts.
Context creation is optimized in the VM in most Smalltalks, so it's
only really created as an object in the environment (reified) when
it's specifically needed through "thisContext". You may emulate its
usage in VisualAge writing something like
[] homeContext
and in a method it would be
>>thisContext
"returns the context of the sender"
^[] homeContext sender
although with some limitations.
There are several applications related with computational reflection
(Reflective Programming, Meta-Programming, MOP, etc) which makes use
of the current context.
Cheers,
Hernán
> BTW, if this is not the appropriate place for a thread like this, then
> please tell me where I should put it (politely, of course :-p)
> --
> Cheers,
> Peter
>
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