php equivalent to perl's || behavior?

[Coder Droid]

one feature of perl I'm desparately missing in php is using || to assign
the first non-empty value in a list to a variable. For example,

# perl example 1
$a = 1;
$b = 2;
$c = $a || $b;
print $c; # displays 1

# perl example 2
$a = 1;
$b = 2;
$c = $d || $b;
print $c; # displays 2, since $d is empty

# perl example 3
$a = 'apple';
$b = 'banana';
$c = 'cherry';
$d = $a || $b || $c;
print $d; # displays 'apple';

# perl example 4
$a = '';
$b = '';
$c = 'cherry';
$d = $a || $b || $c;
print $d; # displays 'cherry';

This is such a handy language construct. Is there any such php
equivalent that accomplishes this? I've already written a function to do
it. (Like this: $d = value($a, $b, $c). But making value() visible
everywhere is something I'd rather avoid if there's something built-in
to php.)

--cd

[Chung Leong]

Re: php equivalent to perl's || behavior?


"Coder Droid" <coderdroid@lik ethiswouldstops pam.hotmail.com > wrote in
message news:PsJad.1959 5$iC4.16000@fe2 .texas.rr.com.. .[color=blue]
> one feature of perl I'm desparately missing in php is using || to assign
> the first non-empty value in a list to a variable. For example,
>
> # perl example 1
> $a = 1;
> $b = 2;
> $c = $a || $b;
> print $c; # displays 1
>
> # perl example 2
> $a = 1;
> $b = 2;
> $c = $d || $b;
> print $c; # displays 2, since $d is empty
>
> # perl example 3
> $a = 'apple';
> $b = 'banana';
> $c = 'cherry';
> $d = $a || $b || $c;
> print $d; # displays 'apple';
>
> # perl example 4
> $a = '';
> $b = '';
> $c = 'cherry';
> $d = $a || $b || $c;
> print $d; # displays 'cherry';
>
> This is such a handy language construct. Is there any such php
> equivalent that accomplishes this? I've already written a function to do
> it. (Like this: $d = value($a, $b, $c). But making value() visible
> everywhere is something I'd rather avoid if there's something built-in
> to php.)
>
> --cd
>[/color]

No, unfortunately.[color=blue]
>[/color]

[CJ Llewellyn]

Re: php equivalent to perl's || behavior?

"Coder Droid" <coderdroid@lik ethiswouldstops pam.hotmail.com > wrote in
message news:PsJad.1959 5$iC4.16000@fe2 .texas.rr.com.. .
-snip-[color=blue]
> # perl example 4
> $a = '';
> $b = '';
> $c = 'cherry';
> $d = $a || $b || $c;
> print $d; # displays 'cherry';
>
> This is such a handy language construct. Is there any such php
> equivalent that accomplishes this? I've already written a function to do
> it. (Like this: $d = value($a, $b, $c). But making value() visible
> everywhere is something I'd rather avoid if there's something built-in
> to php.)[/color]

The closest that php comes is the Ternary Operator

http://uk.php.net/operators.comparison

[Coder Droid]

Re: php equivalent to perl's || behavior?

> > This is such a handy language construct. Is there any such php[color=blue][color=green]
> > equivalent that accomplishes this? I've already written a function[/color][/color]
to do[color=blue][color=green]
> > it. (Like this: $d = value($a, $b, $c). But making value() visible
> > everywhere is something I'd rather avoid if there's something[/color][/color]
built-in[color=blue][color=green]
> > to php.)
> >
> > --cd
> >[/color]
>
> No, unfortunately.[/color]

Hmmm... that isn't the answer I wanted. ;) But, it's the one I
expected. I thought I'd pretty much exhausted my search for something.

The function I wrote to do this is:

function value()
{
$numargs = func_num_args() ;
for ($i = 0; $i < $numargs; $i++) {
$value = func_get_arg($i );
if ($value != '') {
return $value;
}
}
}

Which obviously loops though all values and returns the first non-empty
one. I use this to determine the value for something when the source
value might come from one of a number of places. e.g., let's say I'm
trying to set the default language, I might use it like this:

$a = value($_REQUEST['lang'], $config['lang'], $_ENV['lang'], 'en');

This allows a number of fallback values. While it works, it is about 200
bytes, which is a hundred times larger than "||". And since it's a
function, I've got to worry about its visibility everywhere. Right now,
it's a method of an object.

Hmmmm.... well, okay. I'm done thinking out loud. Guess I'll ponder the
best way to do this some more.

--cd

[Berislav Lopac]

Re: php equivalent to perl's || behavior?

On Tue, 12 Oct 2004 13:09:13 GMT, Coder Droid wrote:
[color=blue]
> The function I wrote to do this is:
>
> function value()
> {
> $numargs = func_num_args() ;
> for ($i = 0; $i < $numargs; $i++) {
> $value = func_get_arg($i );
> if ($value != '') {
> return $value;
> }
> }
> }
>
> Which obviously loops though all values and returns the first non-empty
> one. I use this to determine the value for something when the source
> value might come from one of a number of places. e.g., let's say I'm
> trying to set the default language, I might use it like this:
>
> $a = value($_REQUEST['lang'], $config['lang'], $_ENV['lang'], 'en');
>
> This allows a number of fallback values. While it works, it is about 200
> bytes, which is a hundred times larger than "||". And since it's a
> function, I've got to worry about its visibility everywhere. Right now,
> it's a method of an object.[/color]

This might be a bit smaller:

function value() {
foreach(func_ge t_args() as $a) {
if($a != '') return $a;
}
}

Berislav

[Coder Droid]

Re: php equivalent to perl's || behavior?

> function value() {[color=blue]
> foreach(func_ge t_args() as $a) {
> if($a != '') return $a;
> }
> }[/color]

True. And that does look cleaner, so I'll probably use that. But it's
still a function, so I still have my visibility problems. I just hate
having to use "global $whatever" every time I want to declare this
object to access this method.

So I'm thinking about (just this once) having one function defined
outside of all my objects (a "supergloba l function" of sorts) and
declaring it at the beginning. Hmmmm... I might give it a shot and see
how it turns out. Sometimes it's hard to tell without a test drive.

--cd

[Berislav Lopac]

Re: php equivalent to perl's || behavior?

On Tue, 12 Oct 2004 20:37:25 GMT, Coder Droid wrote:
[color=blue]
> True. And that does look cleaner, so I'll probably use that. But it's
> still a function, so I still have my visibility problems. I just hate
> having to use "global $whatever" every time I want to declare this
> object to access this method.
>
> So I'm thinking about (just this once) having one function defined
> outside of all my objects (a "supergloba l function" of sorts) and
> declaring it at the beginning.[/color]

Which is a completely legal approach in PHP.

Berislav

[Markus Ernst]

Re: php equivalent to perl's || behavior?

Coder Droid wrote:[color=blue][color=green]
>> function value() {
>> foreach(func_ge t_args() as $a) {
>> if($a != '') return $a;
>> }
>> }[/color]
>
> True. And that does look cleaner, so I'll probably use that. But it's
> still a function, so I still have my visibility problems. I just hate
> having to use "global $whatever" every time I want to declare this
> object to access this method.
>
> So I'm thinking about (just this once) having one function defined
> outside of all my objects (a "supergloba l function" of sorts) and
> declaring it at the beginning. Hmmmm... I might give it a shot and see
> how it turns out. Sometimes it's hard to tell without a test drive.[/color]

I use a class which works as a container for all my functions I want to see
globally, and let all other classes inherit it; so that kind of function is
visible everywhere.

class functions
{
function value()
{
[...]
}
}

class otherclass extends functions
{
function use_value($a, $b, $c)
{
return $this->value($a, $b, $c);
}
}

And also in the calling script you can use $otherclass->value() as soon as
you have an instance of otherclass.

HTH
Markus

[Coder Droid]

Re: php equivalent to perl's || behavior?

> > So I'm thinking about (just this once) having one function defined[color=blue][color=green]
> > outside of all my objects (a "supergloba l function" of sorts) and
> > declaring it at the beginning.[/color]
>
> Which is a completely legal approach in PHP.[/color]

And which is what I ended up doing. It's not too bad, actually.

--cd

[Coder Droid]

Re: php equivalent to perl's || behavior?

> I use a class which works as a container for all my functions I want
to see[color=blue]
> globally, and let all other classes inherit it; so that kind of[/color]
function is[color=blue]
> visible everywhere.[/color]

Hmmm... hadn't thought of trying that either. Thanks for the tip.

--cd