[SR-Dev] new operators & if($v) behaviour

[Miklos Tirpak]

Hi,

On 04/24/2009 06:44 PM, Juha Heinanen wrote:
> Miklos Tirpak writes:
> 
>  > Both of them would return false. Btw, I do not think that empty value is 
>  > allowed for to tag, it's a very rare case, and could be covered with 
>  > some explicit check.
> 
> to me to tag was just an example of some variable.
> 
>  > We used to write this, but had lots of issues. The problem happens for 
>  > example with @contact.uri.user, when there is no contact header. 
>  > Unfortunately the select function can return and error instead of 
>  > success with "" value in this case. (The can be also revisited) And 'if 
>  > (@contact.uri.user == "")' would evaluate to false because the left had 
>  > side value does not exist, which is wrong.
> 
> this is exactly my point.  you have to first check if something exists
> before you start to compare its value to something.

Yes, this could work, but than we need two checks in most of the cases:

if (defined($v) && ($v != "")) {...}

This is more precise indeed, but the script writer should not forget the 
extra checks.
Regarding SER selects, if we go for this solution, I think we should 
revisit all the select functions. For example @foo.param.abcd should 
return "" only if the 'abcd' parameter of header 'foo' exists, but it's 
value is empty. Than we could simply check the existence of the parameter:
if (defined(@foo.param.abcd)) {...}

Miklos

> 
> -- juha