Hello Jürgen,
In my work to implement the variable viewer, I need some information from
you, if you are willing to share.
When the user closes the last trace window for a symbol, the system needs
to unregister the listener for this symbol. This means I need to know what
I can use to uniquely identify a symbol.
Since there can be multiple symbols with the same name in different
workspaces, I clearly can't use the name as identifier.
The easiest thing to use would of course be the pointer to the
Symbolinstance itself. However, I don't know if I can rely on this
never
changing. Can this instance ever be changed? I.e. can I use &symbol as a
key into a std::map that tracks all active listeners?
Regards,
Elias
On 15 February 2014 19:55, Elias Mårtenson <loke...@gmail.com> wrote:
> 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 variablenamewhich
>> 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
>>
>>
>>
>
