Re: passing refs to subs


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Re: passing refs to subs

by indigo (Scribe)

on Oct 10, 2000 at 00:54 UTC ( [id://35991]=note: print w/replies, xml )

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in reply to passing refs to subs

You have to ask yourself what is slower...passing the array/hash, or the extra deference everytime you assess it. Typically, passing by reference is a win, but now always.

Remember:

    $foo{'bob'};
[download]

is faster than:

    $bar->{'bob'};  # Slower, extra dereference
[download]

So if you have a small array/hash, and dereference it alot, code it both ways, and see what Benchmark tells you. I'm betting the difference will be small enough, you should be optimizing for readability instead.

Also, remember using reference allows you to modify the actual variable, where normally you will just modify a copy. This, and not performance, will usually determine which you should use.

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(Ovid) RE(2): passing refs to subs
by Ovid (Cardinal) on Oct 10, 2000 at 01:47 UTC

Also, remember using reference allows you to modify the actual variable, where normally you will just modify a copy.

I'm sure you understand what really happens in a sub, but your wording is a bit vague, so I'll clarify this for monks who might not be familiar with this issue.

You will only modify a copy of a variable passed to a sub if you copy the arguments to new variables. If you modify the @_ array directly, you modify the original variables. Run the following snippet to see what I mean:

#!/usr/bin/perl -w
use strict;

my $test = "Hi there!";
change($test);
print $test;

sub change {
    $_[0] = "Hey, this is different!\n";
}
[download]

Cheers,
Ovid

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