[Asterisk-Dev] Adding set and backref functionality to the function syntax.

[Jerris, Michael MI]

> Jerris, Michael MI
> 
> Drumkilla is working on correcting this issue.  This 
> conversation brings up another part of functions which is 
> less optimal than the application way of doing things.  We 
> now need to do the lookup twice, one time to check if it is 
> null (once that issue is fixed) and a second time to get the 
> acutal value.  Can anyone come up with a good syntax and 
> functionality within the fuctions structure that would allow 
> for performing the fuction only once, but allowing multiple 
> branches of action based upon the result of a function check. 
>  Perhapse allowing a set somehow within the function parsing. 
>  Something roughly (although obviously the syntax is totally 
> pseudo here) like this:
> 
> Dial(If(Isnull(x=DB(Key\${Exten})?SIP\100:${x})|15|t)
> 

Gotta love quoting yourself.  In discussions this evening with drumkilla
(Russell) and Corydon (Tilghman) we came up with the following to toss
around for syntax both to setvar within a function block, and the
ability to backref a var from the same line in the dialplan, essentially
a variable that lives only in that line.  Please provide comments on the
format.  Parsing should be fairly low hit within the code that searches
for the function name.  


${x=DB(foo/${EXTEN})} would set the variable x to the return of the DB
function, and the entire expression would evaluate just like
${DB(foo/${EXTEN})}
${\x=DB(foo/${EXTEN})}would set the backref var \x to the return of the
DB function, and the entire expression would evaluate just like
${DB(foo/${EXTEN})}.  \x would live only in the parsing of that line in
the dialplan.

Examples:

${IF(${ISNULL(${x=DB(foo/${EXTEN})})}?other:${x})} for setvar
${IF(${ISNULL(${\x=DB(foo/${EXTEN})})}?other:${\x})} for backref

Mike