RE : Copying a hash-of-hashes

> -----Message d'origine-----
> De=A0: Peter Rabbitson [mailto:rabbit@rabbit.us]
> Envoy=E9=A0: jeudi 30 d=E9cembre 2004 04:58
> =C0=A0: beginners@perl.org
> Objet=A0: Copying a hash-of-hashes
>=20
> Hello List,
> To explain the problem I am having, I wrote a simple snipet that
doesn't
> do
> anything meaningful other than illustrating the behaviour I want to
avoid:
>=20
> my %hoh =3D (
>             1 =3D> {
>                 a =3D> 5, b =3D> 5
>                 },
>=20
>             2 =3D> 5
>            );
>=20
>=20
> my @res =3D &RANDOMSUB;  #call a random subroutine
>=20
> print "$hoh{1}{a}  $hoh{2} \n";
>=20
>=20
> sub RANDOMSUB {
>     my %hohcopy =3D %hoh;
>=20
>     $hohcopy{1}{a} =3D 2;
>     $hohcopy{2} =3D 2;
> }
>=20 
local
> hash
> %hohcopy all the values assigned to it have no meaning in the main
body.
> However the print produces 2, 5 instead of the desired 5, 5. As far as
my
> understanding goes this is due to the fact that $hohcopy{1} holds a
> reference to $hoh{1} instead of recreating it's internal structure
> entirely
> from the root to the leaves while performing a copy.
>=20
> The question is whether there is an elegant way to produce a complete
copy
> of a hash-of-hashes-of-hashes-...-of-hashes for internal subroutine
> purposes
> and make sure that all references will be translated properly as well,
> leaving the subroutine no ability to modify the main hash.
>=20
> Thank you.
>=20

Hello,

This is well known behavior.
Try google on "deep copy" ...

On elegant way I know to do a "deep copy" in Perl
is to use dclone method of Storable module.

Something =E0 la:

use Storable qw(dclone);
my $hohcopy_ref =3D dclone \%hoh;

HTH,

Jos=E9.