What is "doIt" anyway?

doIt is a method(right?) that appears in the walkback or debugger but
has no definition nor reference, even for the time when break point in
reached. If it were a temporary method compiled before the run and
removed after, it should be defined somewhere at the time the running
was halted. But it is not.

What is doIt?
Where is doIt?

Best Regards,
Howard

Howard,

> What is doIt?
> Where is doIt?

;-)

It's not a real method, it just looks like one...

If you look down the debug stack to just below #doIt you'll see that the
workspace compiles the expression to be evaluated, creating a
CompilationResult.  The compilation result contains the compiled code as its
#method (it isn't really a method, that's just the name it's given in this
context since the most important use of the compiler /is/ to create methods). .
That "method" is actually an instance of CompiledExpression (as you'll see in
the inspector).  CompiledExpression and CompiledMethod are subclasses of
CompiledCode, and share a lot of similarities.  If you inspect the particular
instance of CompiledExpression you'll see that its "selector" is 'doIt'.
There's no very obvious reason why a CompiledExpression has to have a selector
at all (it could be that only CompiledMethods had them); I suspect it's there
to make the debugger and/or VM simpler since they can treat "real" methods and
CompiledExpressions identically.

The "selector" itself has been generated by the compiler, and I is  (as far as
I know) entirely arbitrary. You can even change it in the debugger to, say,
'some stuff evaluated in a workspace', and restart the evaluation.  In that
case the debugger's stack pane will show that you are executing a "method"
called "some stuff evaluated in a workspace" ;-)

I think that some Smalltalk implementations do implement the do-it
functionality by adding a real (but temporary) method to some class or other.
I can't remember the details, I'm afraid, but it seems very much a hack to
me....

    -- chris