30 May
2009
30 May
'09
5:16 a.m.
this line gives me syntax error:
if ($fU == null) {
how should it be written?
-- juha
11:52 a.m.
On Jun 01, 2009 at 17:48, Juha Heinanen <jh(a)tutpro.com> wrote:
Andrei Pelinescu-Onciul writes:
No, there are very minor differences:
!defined $fU fastest
$fU == "" - extra string conversion
$fU == $null slowest (has to go through a pv call and string or integer
conversion)
Andrei
I thing
if ($fU == $null)
or better:
if (!defined $fU)
just for curiosity, is performance of the above two equivalent?
11:56 a.m.
Andrei Pelinescu-Onciul writes:
No, there are very minor differences:
!defined $fU fastest
ok, please change the syntax.
$fU == "" - extra string conversion
this i don't understand. if i assign $something = "", then $something
is defined and test defined $something should return true.
$fU == $null slowest (has to go through a pv call and
string or integer
conversion)
-- juha
12:19 p.m.
On Jun 01, 2009 at 18:59, Juha Heinanen <jh(a)tutpro.com> wrote:
Juha Heinanen writes:
no
> !defined $fU fastest
one more question related to this: how do i make a variable
"undefined"? is there a function uset($foo) or undefine($foo) or do i need to use slow method
$foo = $null
Yes, assign anything that is undefined, e.g.:
$foo = $undefined_value will work too.
Andrei
12:24 p.m.
On 06/01/2009 07:19 PM, Andrei Pelinescu-Onciul wrote:
--
Daniel-Constantin Mierla
http://www.asipto.com/
On Jun 01, 2009 at 18:59, Juha Heinanen
<jh(a)tutpro.com> wrote:
just for PV case, there is a function exported by pv module pv_unset("$pv"):
http://sip-router.org/docbook/sip-router/branch/master/modules_k/pv/pv.html…
Cheers,
Daniel
Juha Heinanen writes:
no
> !defined $fU fastest
one more question related to this: how do i make a variable
"undefined"? is there a function uset($foo) or undefine($foo)
or do i need
to use slow method
$foo = $null
Yes, assign anything that is undefined, e.g.:
$foo = $undefined_value will work too.
Andrei
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12:32 p.m.
Daniel-Constantin Mierla writes:
just for PV case, there is a function exported by pv
module
pv_unset("$pv"):
http://sip-router.org/docbook/sip-router/branch/master/modules_k/pv/pv.html…
thanks, that made it.
-- juha
12:34 p.m.
On 06/01/2009 07:32 PM, Juha Heinanen wrote:
Daniel-Constantin Mierla writes:
welcome, anyhow, what Andrei suggested works as well, e.g., $ab = $null;
$ab = $some_undef_pv;
Daniel
--
Daniel-Constantin Mierla
http://www.asipto.com/
just for PV case, there is a function exported by
pv module
pv_unset("$pv"):
http://sip-router.org/docbook/sip-router/branch/master/modules_k/pv/pv.html…
thanks, that made it.
12:44 p.m.
On 06/01/2009 07:37 PM, Juha Heinanen wrote:
Daniel-Constantin Mierla writes:
well, the execution speed in this case is not a concern at all. You can
check with benchmark the difference.
Cheers,
Daniel
--
Daniel-Constantin Mierla
http://www.asipto.com/
welcome, anyhow, what Andrei suggested works as
well, e.g., $ab = $null;
$ab = $some_undef_pv;
yes, but i assume that that is again slower because of the pv lookup.
12:15 p.m.
On Jun 01, 2009 at 18:56, Juha Heinanen <jh(a)tutpro.com> wrote:
== is for comparisons not for assignment. If I compare an undefined
value with "" in most languages is true.
Andrei Pelinescu-Onciul writes:
If you mean defined ($fU), instead of defined $fU, I prefer defined $fU
(is more perl-like) and defined ($fU) or defined($fU) works anyway.
No, there are very minor differences:
!defined $fU fastest
ok, please change the syntax. $fU == "" - extra string conversion
this i don't understand. if i assign $something = "", then $something
is defined and test defined $something should return true.
> $fU == $null slowest (has to go through a pv call and string or integer
> conversion)
Andrei
12:27 p.m.
Andrei Pelinescu-Onciul writes:
empty string "" is a very well defined string value. it has nothing to
do with UNDEFINED. i could accept that it would be consider FALSE in a
test, but not UNDEFINED.
regarding "most languages", perhaps perl is such, but even in php, ""
value is a defined (set) value:
$var = '';
// This will evaluate to TRUE so the text will be printed.
if (isset($var)) {
echo "This var is set so I will print.";
}
how do we solve this problem? cast a vote or what?
-- juha
If you mean defined ($fU), instead of defined $fU, I
prefer defined $fU
(is more perl-like) and defined ($fU) or defined($fU) works anyway.
great, i tested and also defined($fU) works!
this i
don't understand. if i assign $something = "", then $something
is defined and test defined $something should return true.
== is for comparisons not for assignment. If I compare an undefined
value with "" in most languages is true.
3 Jun
3 Jun
1:06 p.m.
On Jun 01, 2009 at 19:27, Juha Heinanen <jh(a)tutpro.com> wrote:
Andrei Pelinescu-Onciul writes:
empty string "" is a very well defined string value. it has nothing to
do with UNDEFINED. i could accept that it would be consider FALSE in a
test, but not UNDEFINED.
Think of it as automatic conversion.
If you mean defined ($fU), instead of defined
$fU, I prefer defined $fU
(is more perl-like) and defined ($fU) or defined($fU) works anyway.
great, i tested and also defined($fU) works!
this i
don't understand. if i assign $something = "", then $something
is defined and test defined $something should return true.
== is for comparisons not for assignment. If I compare an undefined
value with "" in most languages is true.
regarding "most languages", perhaps perl is such, but even in php,
""
value is a defined (set) value:
$var = '';
// This will evaluate to TRUE so the text will be printed.
if (isset($var)) {
echo "This var is set so I will print.";
}
This will evaluate to TRUE also in sip-router (if (defined($var))).
The question is how is if ($foo == "") evaluated when $foo is
undefined in php.
how do we solve this problem? cast a vote or what?
Why would you want sip-router to behave differently then other scripting
languages?
I agree that comparing with undefined is and undefined operation so any
solution is more a matter of convention then logic (from a strictly
logical point of view it should throw an error), but since the
convention and what most people expect is that comparing and undefined
value to "" should return TRUE, why innovate?
Andrei
2:11 p.m.
Andrei Pelinescu-Onciul writes:
fine if defined($var) on $var = "" is true.
$var =
'';
// This will evaluate to TRUE so the text will be printed.
if (isset($var)) {
echo "This var is set so I will print.";
}
This will evaluate to TRUE also in sip-router (if (defined($var))).
The question is how is if ($foo == "") evaluated when $foo is
undefined in php. Why would you want sip-router to behave differently
then other scripting
languages?
i don't want that. in php
unset($foo);
if ($foo == "") {
echo "yes\n";
} else {
echo "no\n";
}
prints "yes", but
unset($foo);
if ($foo === "") {
echo "yes\n";
} else {
echo "no\n";
}
prints "no".
=== operator thus allows me to tell, if a var is undefined or assigned
"" value.
== is not good for testing if variable is defined, which prompted this
discussion:
!defined $fU fastest
$fU == "" - extra string conversion
$fU == $null slowest (has to go through a pv call and string or integer
conversion)
so the middle one is not ok for that purpose, but it doesn't need to be
because defined() exists.
-- juha
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days inactive
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17 comments
4 participants
participants (4)
-
Andrei Pelinescu-Onciul -
Daniel-Constantin Mierla -
Jan Janak -
jh＠tutpro.com