[SR-Dev] script parsing: string switch support

[Daniel-Constantin Mierla]

On 02/20/2009 04:54 PM, Henning Westerholt wrote:
> On Friday 20 February 2009, Andrei Pelinescu-Onciul wrote:
>   
>> [..]
>>     
>>>> (1) - could be changed in some cases (e.g. string case with some int
>>>> label allowed, which could be automatically converted to string), but I
>>>>  think it would too confusing and I disallowed it (in general having
>>>>  mixed types in a switch() are 99% an error).
>>>>         
>>> I would suggest to convert numbers to strings in this case automatically.
>>> For most people things get more confusing with the increasing amount of
>>> details they have to remember about the configuration language.
>>>       
>> This would only make sense if we use match() for strings and switch()
>> for ints. Otherwise it would be too confusing.
>> Anyway I don't think the amount of details of the configuration language
>> is ever a problem, as long as one gets meaningful error messages when
>> checking the config (and before ser startup).
>>     
>
> Hi Andrei,
>
> the amount of detail in the config language is IMHO important. The developers 
> must document and test every single statement. Every user must read, learn 
> and memorize each statement too. 
>
> I regulary need to check the documentation for some special cases in the 
> config when i get asked for a review of some changes a co-worker did, because 
> he still feel not completely confortable after years of administrating SER* 
> systems. During all the time i spend on user channels i really rarely heard 
> the that our server is to slow (only when some real bottlenecks were 
> involved, like DB), the common complain is that the learning curve is too 
> steep. Perhaps i'm lazy, but i'd not say that everybody out there is it 
> too. ;-)
>
>   
>> The other approaches trade-off less config details for guessing what the
>> user intended, which IMO is much more dangerous. Is much better to get
>> meaningful errors when running ser -cf ... , then getting unexpected
>> behaviour at runtime (a very good example for this are typed variables
>> vs. untyped ones or operators that try to guess the type and assume the
>> user made the right choice).
>>     
>
> I just checked in kamailio, we don't throw an error if one mix strings and 
> ints in a switch case.
this is because the most of PVs have the string value as well.

However, I consider that misleading, although I worked a lot the switch. 
It was planned to fix as the PV callbacks had a parameter for flags.

I would prefer single type case value, and report errors at startup - it 
is easier to check and optimize. It is better to use a transformation to 
convert the value to a specific type (e.g., {s.int}).

Cheers,
Daniel

>  We also check for a correct type of an integer in a 
> mixed expression, e.g. if its a valid int value. I don't think that we 
> convert them implicitly, as many pseudo-variables hold internally both a 
> string and a integer value, so mixed expression will work just as intended in 
> most cases.
>
> Cheers,
>
> Henning
>
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>   

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