Re: Simple Pass By Reference

Try this.

It uses a prototype to save you from explicitly taking a reference when you call the sub.

It assigns the reference to a localised glob to avoid the need for explicit dereferencing inside the sub.

It uses our to satisfy strict.

Result: Efficient pass-by-reference without the pain of dereferencing.

#! perl -slw
use strict;

sub modify (\$) {
    our $data;
    local *data = $_[ 0 ];

    $data =~ s[this][that]g;
    return;
}

my $string = 'this & that;' x 10000;

modify $string;

print substr $string, 0, 24;
[download]

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Comment on Re: Simple Pass By Reference Download Code

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Re^2: Simple Pass By Reference by cosimo (Hermit) on Jul 26, 2005 at 16:01 UTC
I would really drop the `our` and `typeglob` usage here. I feel like it's "overkill" for what [id://tomazos] is trying to do. The following is also an interesting solution, that is quite similar to [id://friedo]'s one, but uses prototype to move referencing backslash from main script into the function code. #!/usr/bin/perl use strict; use warnings; sub modify (\$) { my $string_ref = $_[0]; $$string_ref =~ s/a/x/g; } my $string = 'abc'; print "before `$string'\n"; # abc modify $string; print "after `$string'\n"; # xbc [download] Anyway, probably it is best to leave the `\` char inside the main script. In this way, it is immediately clear that you're passing a reference, and not the real scalar. In the latter case, you could be tempted to think that a return value is also expected from the `modify()` function, which actually is not.	[reply] [d/l] [select]
Re^3: Simple Pass By Reference by tomazos (Deacon) on Jul 26, 2005 at 17:27 UTC
Sure, that's using referencing/dereferencing - which is fine, but I'd rather have a normal scalar name ($string rather than $$string_ref). In this example its trivial, but if you have a lot of variables around, its hard to keep track of whats a reference and whats not. -Andrew. Andrew Tomazos \| andrew@tomazos.com \| www.tomazos.com	[reply]