[sr-dev] replacing k pvars with s selects

[Daniel-Constantin Mierla]

On 07/03/2009 07:02 PM, Andrei Pelinescu-Onciul wrote:
> On Jul 03, 2009 at 18:45, Daniel-Constantin Mierla <miconda at gmail.com> wrote:
>   
>> On 07/03/2009 06:36 PM, Juha Heinanen wrote:
>>     
>>> Daniel-Constantin Mierla writes:
>>>
>>>       
>>>> whose confusion? 
>>>>         
>>> like the discussion on lookup_domain function revealed, it is confusing
>>> that the same prefix ($ char) is used for two different things.
>>>  
>>>       
>> from my point of view, all are script variables: avps, references to sip 
>> message parts, etc ... therefore the have to start with same char, and 
>> most of the programming languages use $ for that. It is what was decided 
>> long time ago in openser when pseudo-variables were introduced in core.
>>     
>
> >From my point of view the only things that are close to variables are
> the avps

avps are not at all, if you put it this way. it is a linked list, 
actually more like a stack, but via some options, elements that are not 
in top, can be accessed.



>  and the script vars. All the others are in fact hidden function
> calls and should be syntactically different.
>   
All are function calls as long as the value can be int or string.


>> Basically, there are classes of script variables, some accepting dynamic 
>> names (like avps $avp(...), headers $hdr(...), private $var(...) and 
>> shared variables $sht(...) a.s.o.).
>>
>> I do not see reason for a special character for certain classes, like 
>> avp or select. It is much much clearer to have:
>> $avp(name)
>> $sel(name)
>>     
>
> We should use $ only for variables (like any other script language out
> there). This doesn't mean avps though. The avps should be accessed in
> some other distinct way. avps are both slow and they consume memory, so
> their use as script vars should be discouraged.
>
>   
>> rather than:
>> $name for avps
>> @name for selects
>> &name, %name etc. for what so ever variable class
>>     
>
> I would use '$' only for fast script vars (that should be declared at
> the beginning of the script and would be typed), and some function like
> construct for the other (e.g.  $var=sel("from.uri")).
>   

in shell you can have ${VAR:0:5}. Introducing of PV in openser core 
started from %name used in xlog, but trying to follow shell var syntax.

Besides just nice to discuss, such changes makes no point now. Remember 
the goal is to have a first version for each project that is easy to 
migrate to from older ones. Therefore we committed to go for a best 
compatibility approach. I hope we do not divert from here, otherwise 
will be come a nightmare to get people on board with migration.

If someone has free time, no problem, he can start coding a new 
framework that could obsolete PVs (and selects, a.s.o.) via better 
design and functionality, keep both for a while, let other developers 
update their code to the one that is more appealing and the users become 
comfortable with syntax, etc...

PV framework impact to core is very minimalistic, I hoped same would 
happen with selects, but not yet. Where two fit, it is place for the 
third...

Daniel

-- 
Daniel-Constantin Mierla
http://www.asipto.com/