in reply to Re: Simple Pass By Reference
in thread Simple Pass By Reference

That duplicates the content of $_[0] doesn't it? (Your first example)

I want to pass it by reference, and give it a meaningful identifier in the context of the subroutine. (ie not have to use $_[0] throughout the subroutine.) (Your second example)

-Andrew.

Andrew Tomazos  |  andrew@tomazos.com  |  www.tomazos.com

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Re^3: Simple Pass By Reference
by friedo (Prior) on Jul 26, 2005 at 00:12 UTC
    You can use a simple scalar reference, then. 

    sub alter_var { 
    my $scalar_ref = shift;
    $$scalar_ref =~ s/a/b/;
}

my $scalar = "foobarbaz";
alter_var( \$scalar );

    [download]

    For more, see perlreftut.

    Also note that esskar's second example, which works on $_[0] directly, will alter the scalar passed into the parameter list. (In this case, $_[0] is an alias, not a reference, so there is no need to dereference anything.)

[reply]
[d/l]
      I kind of wanted to use a local alias for $_[0], rather than have to use a reference that I have to remember to dereference everywhere.

      I guess I just want to say: 

          alias $var_in_sub = $_[0];

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      Just to give $_[0] a meaningful name in the context of the subrountine, such that $var_in_sub and $_[0] are the same thing. In the same way as $var_elsewhere and $_[0] are the same thing when calling alter_var($var_elsewhere).

      I guess this can't be done in Perl, without using references and dereferencing - which is fine. No big deal.

      -Andrew.

      Andrew Tomazos  |  andrew@tomazos.com  |  www.tomazos.com
[reply]
[d/l]
[select]
        Wouldn't this be considered to be semi-alias? Well you create one more variables but still does not have the "contents" as it is still a pointer/reference. So memory is OK here?

        sub alter_var {
    my $aliasvar = $_[0];    # Nice to have C like proto types but...
    ${$aliasvar} =~ s/a/b/g;
#   ${$_[0]} =~ s/a/b/g;   # This uses $_[0] and works
}

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[reply]
[d/l]
        I guess this can't be done in Perl, without using references and dereferencing - which is fine. No big deal.
        Someone always has to dereference. I'm not sure, but I think you're after one of the alias modules (Lexical::Alias, Tie::Alias, Variable::Alias, Data::Alias).

        MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"
        I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).
        ** The third rule of perl club is a statement of fact: pod is sexy.

[reply]

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