[Oorexx-rfes] [ oorexx-Feature Requests-3194813 ] Add support for ::attribute myAttribute raise novalue

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Feature Requests item #3194813, was opened at 2011-02-28 03:26
Message generated for change (Comment added) made by bigrixx
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Category: Interpreter
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: jfaucher (jfaucher)
Assigned to: Nobody/Anonymous (nobody)
Summary: Add support for ::attribute myAttribute raise novalue

Initial Comment:
::attribute myAttribute raise novalue

An ::attribute with default 'get' implementation never raises NOVALUE.
You have to provide your own 'get' implementation like that :
::attribute myAttribute get
    expose myAttribute
    signal on novalue
    return myAttribute
    novalue:
    raise propagate

I propose to let support this kind of declaration :
::attribute myAttribute raise novalue
which will automatically generate the code above.

>>-::ATTRIBUTE--name--+---------------+----
                      +-RAISE NOVALUE-+
                      +-GET-----------+
                      +-SET-----------+
                      
In complement to RFE 3001080 (Add a NOVALUE switch to ::OPTIONS)
It would be nice if the ::options novalue could change the default 'get' implementation of all methods of the package, as described above.


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>Comment By: Rick McGuire (bigrixx)
Date: 2011-02-28 08:51

Message:
Yes, that RFE would result in that behavior.  I think, in general, SIGNAL
ON NOVALUE is only generally useful for large, monolithic classic-style
programs where a single label target can be used for an entire program. 
Since this really is a debugging/reliability issue, having an option to
make this an error would achieve the same ends. 

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Comment By: jfaucher (jfaucher)
Date: 2011-02-28 08:47

Message:
ok, let's forget the ::attribute raise novalue.

This morning, for debug, I added 'signal on novalue' in each method, and
was surprised to have no error and still see the wrong value MYATTRIBUTE.
Until I understood that I had to add 'signal on novalue' in the
::attributes.

Since I use NOVALUE mainly for debug, what I'm looking for is what you
propose in RFE 3001080.
I suppose that with ::option NOVALUE, an error will be raised when reading
an attribute without value ?
If this is correct, then I will delete my RFE.

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Comment By: Rick McGuire (bigrixx)
Date: 2011-02-28 06:51

Message:
I am generally NOT in favor of this enhancement.  Attributes are NOT
variables, they are methods.  NOVALUE conditions are a variable concept and
are raised only on the current call context.  This just further confuses
the concepts. 

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