[SR-Dev] operators and variables

[Jan Janak]

On 12-12 19:15, Andrei Pelinescu-Onciul wrote:
> On Dec 12, 2008 at 16:41, Jan Janak <jan at ryngle.com> wrote:
> > On 11-12 22:01, Andrei Pelinescu-Onciul wrote:
> > > 
> > > It would be better to have different operators for strings and for
> > > integers. Right now we have '+', '==' and '!=' that can be used both for
> > > strings and integers. The problem with this approach is that it makes
> > > some optimizations impossible, especially when combined with dynamic
> > > typed variables (avps or pvars). '+' is especially bad because one
> > > can tell what type ($v + x) has only at runtime.
> > 
> >   I would like to preserve the original behaviour for strings. They are used
> >   much more often than integers. If you need to change anything then, please,
> >   consider changing the behaviour of integer operators.
> > 
> > > I think having perl like operators would help a lot:
> > > 
> > > - '.' for string concatenation (instead of reusing '+'), e.g.: 
> > >  $v= "foo" .  "bar"
> > 
> >   Yes, I like this one.
> > 
> > > - 'eq' instead of == for strings, e.g.: $v eq "bar" 
> > > - 'ne' instead of != for strings, e.g.: $v ne "bar"
> > 
> >   I don't like this. If there really is a need to have separate operators then
> >   use 'eq' and 'ne' for integers and keep == and != for strings. Test (see man
> >   test) has string and integer operators this way.
> 
> I was using perl as a guideline (since we already have perl like stuff,
> like ~=).

  Yeah, I know, my point was that in SER scripts I've seen we use these
  operators with strings often and hence we should consider to preserve
  the behavior for strings (as opposed to integers). I made the remark 
  about test to show that there are differences in existing scripts (perl 
  versus shell).

> > > We could support them right now in parallel with the old ones and 
> > >  obsolete +, ==  and != for strings in the future (but that means we
> > >  still cannot optimize '+' in all the cases) or switch right now
> > > (maybe with some old compat switch which will support old scripts
> > > style).
> > > The question is how much are they used right now. While I think '==' and
> > > '!=' are used quite often, I'm not sure about '+' for strings (and '+'
> > > is the most important anyway).
> > 
> >   I guess == and != are used most often with strings.
> > 
> > > Note: we can still support '==' and '!='  for condition tests not
> > > involving variables (e.g. method=="INVITE", uri=="sip:foo" a.s.o.).
> > 
> >   That would be inconsistent. if (method=="INVITE") would work, but
> >   if ($abc=="foo") would not work if strings operators are replaced with 'eq'
> >   and 'ne'.
> 
> Yes, it would be, but I was thinking that most people use it only this
> way and hence the change would not affect them immediately.

  I can neither confirm nor deny this, but at least in ser-oob.cfg operator ==
  is used a lot with strings, so this config, at least, would be affected by such
  change.

     Jan.