Calling subroutine:Using &

[spookie]

Hi,
Is it good practice to use & to call a subroutine ?

Your thoughts please.



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I never set a goal because u never know whats going to happen tommorow.

 

[KevinADC]

It's not considered good, but it's not considered bad as far as I know. But you have to know how its use affects programs.

http://perldoc.perl.org/perlsub.html

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- Kevin, perl coder unexceptional!

 

[Kirsle]

I think generally, using & implies to the interpreter that you're calling one of your own subroutines and not one exported by a module or any standard Perl function.

For instance:

sub join {
   my ($channel) = @_;

   $irc->join ($channel);
}

join ("#lobby");

Perl warns
"Ambiguous call to subroutine resolved as main::join() at script.pl line X"

&join ("#lobby");

no Perl warning for that

At least that's how it goes in my experience...

Since join() is a core function, if you define a sub by that name and call it without &, Perl warns you and then assumes you meant your local version of join and not the core method (if you wanted the core method and you had a sub named "join", you have to call it as "CORE::join()" instead).

I'd say it's probably better to use &.

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[spookie]

Thanks for your inputs KevinADC, Kirsle.

I personally never use & while calling sub. But recently i saw couple of scripts with & prefix and i thought, hey this is more readable than not using &.



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I never set a goal because u never know whats going to happen tommorow.

 

[1DMF]

leaving the & off means the interpreter treats the sub as a prototype, I don't understand fully what that means.

But it's like creating a sub that works like an internal command.

also callng a sub with () apprently leaves the current @_ exposed to the called sub.

Something I never knew till today.

This link may help

http://www.unix.org.ua/orelly/perl/prog3/ch06_04.htm

"In complete darkness we are all the same, only our knowledge and wisdom separates us, don't let your eyes deceive you.

 

[1DMF]

opps , that should be

callng a sub withOUT ()

"In complete darkness we are all the same, only our knowledge and wisdom separates us, don't let your eyes deceive you.

 

[stevexff]

Must admit, I've always left off the &, and used the my_sub() notation to call them, which causes perl to behave like most other languages WRT scoping etc. so I've never run across this problem.

But overloading the built-in functions with same-named ones of your own devising (on purpose) sounds like a really bad idea...


Steve

[small]"Every program can be reduced by one instruction, and every program has at least one bug. Therefore, any program can be reduced to one instruction which doesn't work." (Object:erlDesignPatterns)[/small]

 

[KevinADC]

But overloading the built-in functions with same-named ones of your own devising (on purpose) sounds like a really bad idea...

I agree, bad idea. perlsub goes over this quite extensively:

http://perldoc.perl.org/perlsub.htm...Functions-built-in-override-CORE-CORE::GLOBAL

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- Kevin, perl coder unexceptional!