Awesome. I'll add support for this tonight or tomorrow.
Regards,
Elias
On 15 February 2014 19:48, Juergen Sauermann
<juergen.sauerm...@t-online.de>wrote:
> Hi Elias,
>
> I believe deriving from class Symbol is not the right way because there
> can be multiple
> pointers to the original symbol around and when you simply replace a
> symbol in class Workspace
> then you have a mix of the original and the new derived symbol.
>
> I have therefore added a callback function in class Symbol that is called
> on changes of the symbol.
>
> Use it like this:
>
> void my_monitor(const Symbol & symbol, Symbol_Event sev)
> {
> // ...
> }
>
> Symbol * monitored = ...
>
> monitored->set_monitor_callback(my_monitor); // start monitoring
> monitored->set_monitor_callback(0); // stop monitoring
>
> See SVN 124.
>
> /// Jürgen
>
>
>
> On 02/12/2014 05:58 AM, Elias Mårtenson wrote:
>
> I was watching this video where they take advantage of the )ED command in
> Dyalog which supports realtime updated views of a variable:
> http://youtu.be/a9xAKttWgP4?t=5m2s
>
> At 5:02 into the above video, the presenter types )ED variablename which
> opens a window that with the content of a variable. This is a very neat
> feature.
>
> Obviously, I wanted to see the same thing in GNU APL (for myself, I'd
> like to see it in an Emacs buffer). So, I started work on this (exactly
> what method should be used to invoke this feature is a subject for a
> separate email thread which I will post shortly).
>
> The key feature that is needed is a way to be informed when a variable
> is changed. Changes to a variable seems to be done through calls to method
> of Symbol. The key methods are Symbol::assign(), Symbol::assign_indexed()and
> Symbol::push_value().
>
> The approach I started experimenting with is to create a subclass of
> Symbol which provides callback functionality when these methods are
> called, which I can then use to send a message to Emacs when the values are
> changed. I'm not done with this yet, so I'm not ready to say if this say if
> it works fully at this point.
>
> Now, I would like to know three things:
>
> - Is my approach of subclassing Symbol the best way to do it? Assuming
> it is, the question is:
> - How should I create the new subclassed symbol as a copy of the old
> one? Would it make sense to create a copy constructor for this class that
> the subclass can take advantage of?
> - Finally, I'd need to expose a function on Workspace that allows me
> to replace a symbol with my monitorable (is that a word?) version.
>
> I suppose an alternative approach to all of this would be to add the
> callback functionality right into the Symbol class, but that would have
> negative potential performance implications.
>
> What are your thoughts on this?
>
> Regards,
> Elias
>
>
>
