30 Apr
2009
30 Apr
'09
1:02 p.m.
missing attachement added.
On Apr 30, 2009 at 12:53, Andrei Pelinescu-Onciul <andrei(a)iptel.org> wrote:
On Apr 28, 2009 at 13:09, Miklos Tirpak
<miklos(a)iptel.org> wrote:
OK, this could work also in SR. Let's decide whether or not we introduce
another operator for string comparisons ('eq'), or stick to '=='.
I've introduced eq, ne for strings, ieq and ine for integers. The names
are temporary as their intended use is testing (for possible
introduction in the next-next release).
This is ok, this is the way it behaves now (on my type_conversion
branch).
Hi Andrei,
On 04/28/2009 10:33 AM, Andrei Pelinescu-Onciul wrote:
For now we could keep it, but for next releases we need some changes.
We need at least different version for ==, != and + for integer and
strings. Overloading them to work for both is just broken and it will
lead to strange behaviour.
Another important change would be typed variables and avps (we would be
able to do much better error checking on the script and make life much
more easier for script writers at the cost of only having to pre-declare
the vars with the intended use type).
On Apr 28, 2009 at 09:53, Miklos Tirpak
<miklos(a)iptel.org> wrote:
Yes, I understand, but == was not an int operator in SER so far. So the
question is whether or not we want to change the script syntax, or shall
we keep the support for the current scripts. On 04/27/2009 04:18 PM, Juha Heinanen wrote:
>Andrei Pelinescu-Onciul writes:
>
>>We could try some sane defaults (for if ($v)).
>yes, in case there are some.
>
>>For example that's what perl does:
>> undefined "" string 0 other integer
>>
>>$foo eq undef true true false false false
>>$foo == undef true true true true false
>>
>>$foo eq "" true true false false false
>if $foo is undefined, it is insane to me that it would be equal to empty
>string "" or 0. also comparing two undefined things should not result
>in true.
Actually if you think in terms of the operators it's not. The operators
forces conversion of its operands to the type it expects.
so for eq (which used for string): $foo eq undef is in fact
(str) $foo eq (str) undef , and (str) undef is "".
With undefined you have 2 options: either have valid conversion to
string and ints or bail out with an error. Since we cannot stop the
script or abort(), even if we report an error we still have to come up
with a result.
yes, this is really strange indeed. And
("abcd" == undef) is also true
according to the table.
Bear in mind, that == in this case (perl) is an int operator,
so "abcd" == undef is in fact (int) "abcd" == (int) undef and
(int) "abcd" is 0
(int) undef is 0
=> 0 == 0. >what would make sense to me is that comparing
an undefined thing to
>anything that is defined, would result in false.
I agree.
I don't. We have special operators for checking if something is defined
or not. If you don't use it you want implicit conversion.
In almost all script languages, if a var is undefined then it's equal to
"".
If you think some other behaviour is better, please fill all the table
and think also about normal operations, e.g. $v int+ $x, $v str+ $x.
Bear also in mind that we support 2 types: int and str. We don't
support bool (bool is int) so all logical expressions are evaluated to
int (so you cannot say bool("a") == true but int("a")==0).
Also think about how other scripting languages handle that.
What do you think about this? Undef is either 0 or "", and == is used
both for string and int.
undefined "" string 0 other integer
$foo == undef true true false true false $foo == 0 true false false true
false
^^^^^
this is not, but it's related to the
string to int conversion (below)
(The right value is converted to the type of the left value if
necessary. So "0" == 0, but "" != 0.)
bool($foo) false false true false true
^^^^^ we do not have boolean
and I don't think introducing it would be
a good ideea.
int($foo) 0 0/error I/error 0 I
^^^^^^^^^^^^^^^^
right now in my branch it works like this:
at startup you'll get an error (if the type is
known to be string). If the type is not known
(avp pvar) => I can't tell if it's an error or
not,
At runtime it's 0 (for "", "abc") or I
(for "123"). No error is generated (it
wouldn't help anyway, it's too late).
str($foo) "" ""
S "0" "I"
0/error, and I/error means that the expression should be evaluated in
the 'if' conditions, and in the mathematical expressions slightly
differently:
That's what I want to avoid, different behaviour.
if (0 == "") -> false, (0 == "0") would be true.
if (0 == "abcd") -> false
if (1 == "1") -> true
$v + "" -> $v -> I think we have no other choice.
$v + "abcd" -> $v
$v + "1" -> $v + 1
I do not whether or not it's close to any scripting language, feel free
to tell me if it's a complete mess. But I think it's closer to the
current SER script language at least.
I've attached a first draft describing how type conversion and operators
work in sip-router. It describes the code on the andrei/type_conversion
branch. If I won't get strong objections, I'll merge that branch into
master (we can't waste too much time arguing, we need to have something
sane and something that mimics perl behaviour as much as possible it
should be at least good enough).
If people are worried about specific ser or kamailio script snippets
that won't work, then please provide some _simple_ test config that I
can use. By simple, I mean something using very few modules (only xlog &
pv would be ideal) and having something like:
$var=expr_that_might_not_work;
if ($var != expected_value )
xlog("L_CRIT", "BUG: sanity check 1 failed");
if ( expr2 != expectred_value)
xlog("L_CRIT", "BUG: sanity check 2 failed");
a.s.o.
We could collect them and use them for testing each time we do a change
to expression evaluation.
Andrei
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