Refs

[paymon at 365.co.uk]

okay, so it's not worth it then, unless I'm passing the array from hell.
Point taken and being poked as we speak.

Paymon


On Thu, Nov 30, 2000 at 11:08:32AM +0000, Pap Taylor wrote:
> Two things Paym,
> You need to sign up from your work address if you want to post from
> there. southampton-pm has a members only submission thing in action.
> 
> Onto your question:-
> 
> --question
> 
> Anyway here's me spak ladened question my old muckers.
> How does perl pass things in functions?
> E.g.
> $poo = "Bad shagging data structure";
> &myfunct($poo);
> sub myfunct
> {
> Whatever oooh the pain.
> ...
> ...
> }
> 
> Now, does perl pass the information as a reference or does it copy the
> whole thing. In other words would I make my scripts more efficient by
> passing everything by reference?
> Over to the perl meisters.
> 
> --- question
> 
> Perl passes things by copy. It has to. As you know, when Perl calls a
> function, all arguments are passed as a parameter array.
> 
> Perl will create the parameter array as a copy of the original
> data. Passing things by reference will allow subroutine modifications to
> persist after the scope of the sub.
> 
> As for speed, somewhat difficult to say. If you do pass references, you
> obviously don't need to return stuff. If you're returning a scalar, Perl
> would create a temporary scalar behind the scenes before it arrived in your
> return value. If you return an array, Perl will create an temporary array
> to shift the stuff into the values you're assigning the result of the
> function to.
> 
> Yadda yadda yadda.
> 
> It would seem that by passing references, you'd stop Perl from needing to
> create this temporary values. But you'd be wrong. Perl will return
> implicitly if it doesn't return explicitly. It'll return the last thing
> evaluated by default, e.g. the result of the print function or the if
> statement. So whether you return explicitly or not, Perl will still return
> something, even if it's delivering the value to void.
> 
> Remember, that even if you passed your args as refs, Perl would still
> endure the overhead of creating your parameter array.
> 
> The /only/ time I use references to function calls is when there's a damn
> good reason ( i.e. passing nested structures - or multiple lists or hashes
> ). If you're after passing scalars, it isn't worth the bother. Remember
> that each of your refs is a scalar too, and will cause almost as much overhead.
> 
> And I do hope you're using named parameters....
> 
> P
> 
>