Re^2: I have a hash in a hash in a .....

Read-only result? I'm not sure what you mean by that, but if you assign to an element of $r, that affects $my_hash_ref. They're all references so they're pointing at the same data.

#!/usr/bin/perl

use Data::Dumper;

my $hash = {
    a => { ab => { ac => 'fred' }, abb => 'barney' },
    b => 'betty',
    c => { cb => 'dino' },
    };

my $r = $hash;

my @k = qw( a ab );

print Dumper( $hash );

$r = $r->{$_} foreach @k;

$r->{ 'ac' } = 'Mr. Slate';

print Dumper( $hash );
[download]

--
brian d foy <brian@stonehenge.com>
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Re^3: I have a hash in a hash in a ..... by ikegami (Patriarch) on Feb 21, 2006 at 20:37 UTC
You didn't change ~~`$r`~~ the accessed value in your snippet — you changed that which is pointed by `$r` — so you failed to disprove that ~~`$r`~~ the accessed value is read-only. Say you want to do `$my_hash_ref->{$k[0]}->{$k[1]}->{$k[2]} = 3;`. Compare `use Data::Dumper; my $my_hash_ref = { a => { b => { c => 2 } } }; my @k = qw( a b c ); my $r = $my_hash_ref; $r = $r->{$_} foreach @k; $r = 3; print Dumper($my_hash_ref); # { 'a' => { 'b' => { 'c' => 2 } } };` [download] with `use Data::Dumper; my $my_hash_ref = { a => { b => { c => 2 } } }; my @k = qw( a b c ); my $p = \$my_hash_ref; $p = \($$p->{$_}) foreach @k; $$p = 3; print Dumper($my_hash_ref); # { 'a' => { 'b' => { 'c' => 3 } } };` [download] Update: Fixed a terminology error.	[reply] [d/l] [select]
Re^4: I have a hash in a hash in a ..... by brian_d_foy (Abbot) on Feb 21, 2006 at 20:50 UTC
Perhaps you could define "read-only", because I can certainly change $r. I can just assign it a new value. I can change the data it points to. None of those things relate to "read-only". It's the conpletely wrong way to think about it. That `$r` no longer is a reference when I give it another value doesn't really matter. -- brian d foy <brian@stonehenge.com> Subscribe to The Perl Review	[reply] [d/l]
Re^5: I have a hash in a hash in a ..... by ikegami (Patriarch) on Feb 21, 2006 at 20:57 UTC
I said the result was read-only. I never said `$r` was read-only. Oops, I didn't original post, but I did in my second post. Fixed. The OP wanted a means of accessing the value at "key" @k. Using the "$r" method, one cannot edit the accessed value. Using the "$p" method, one can edit the accessed value. When something cannot be edited, it is said to be read-only. So while the scalar `$r` itself is not read-only, the accessed value is read-only. Update: Added underlined text.	[reply] [d/l] [select]