making arrays that act like hashes at runtime

dinesh has asked for the wisdom of the Perl Monks concerning the following question:

hi i want to know wheather we can build an array which will acta s an hash at runtime it is possible otherwise in versions 5.005 and above using the syntax

{key1=>arrayindexvalue1, key2=>arrayindexvalue2,..... }

for example

$arrayreference = [{first =>1,second =>2 } , "hello ","there"];
[download]

now this will work both as an array and a hash

print " $arrayreference->{first} \t  $arrayreference->{second} \n";

>hello there
print " $arrayreference->[1]   \t $arrayreference->[2] \n";


>hello there
[download]

can i build this thype of array at runtime that is can i add elements to this array one by one rather than initializing them all at one time

thanks

dinesh

edited: Mon Jul 1 13:29:48 2002 by jeffa - added code tags

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Re: making arrays that act like hashes at runtime by davorg (Chancellor) on Jul 01, 2002 at 11:55 UTC
Pseudohashes are an exprimental feature that was added in 5.005 and are now widely considered to be a mistake. They will be deprecated in 5.8 and removed completely in 5.10. I therefore recommend that you don't use then for any new development. -- <http://www.dave.org.uk> "The first rule of Perl club is you do not talk about Perl club." -- Chip Salzenberg	[reply]
Re: making arrays that act like hashes at runtime by cjf (Parson) on Jul 01, 2002 at 12:08 UTC
Pseudo-hashes: Using an array as a hash But for reasons already provided, don't use them :).	[reply]
Re: making arrays that act like hashes at runtime by amphiplex (Monk) on Jul 01, 2002 at 12:07 UTC
Just for completeness' sake (as the others here said, it is propably not a good idea to use this 'feature'): a quote from "Object Oriented Perl" by Damian Conway: --- <quote> <quote> You can add new entries to a pseudo-hash, but it's a two step procedure. First, you add a new key-to-index mapping: `$pseudo_hash->[0]->{"z"} = @{$pseudo_hash};` [download] which maps the key "z" onto the first unused index in the pseudo-hash array. After that, you can access the new entry directly, to assign it a value: `$pseudo_hash->{"z"} = "value z";` [download] </quote> ---- </quote> which would translate to something like this in your example: `my $a = [ {first=>1, second=>2}, "hello", "there" ]; print "$a->{first}\t$a->{second}\n"; $a->[0]->{'third'} = @{$a}; $a->{'third'} = "foo"; print "$a->{first}\t$a->{second}\t$a->{third}\n";` [download] ---- kurt	[reply] [d/l] [select]
Re: making arrays that act like hashes at runtime by perrin (Chancellor) on Jul 01, 2002 at 13:45 UTC
You may be able to get what you need by using the enum module. It would let you do this: `use enum qw(first=1 second); my @foo; @foo[first, second] = qw(hello world);` [download] That puts the constants in the package namespace though, which you might not want. It's good for making objects based on array refs. If this isn't what you're after, try ArrayHashMonster.	[reply] [d/l]
Re: making arrays that act like hashes at runtime by bronto (Priest) on Jul 01, 2002 at 13:51 UTC
You could `use fields` and `fields::phash` in particular. Documentation reads: fields::phash() can be used to create and initialize a plain (unblessed) pseudo-hash. This function should always be used instead of creating pseudo-hashes directly. Nevertheless, I subscribe other's advice about not using pseudohashes at all. I don't know if even the `fields` implementation of pseudohashes will disappear or will be the "official way" of using pseudohash-like structures. Is there any monk that could give us an advice on this? Thanks `--bronto` # Another Perl edition of a song: # The End, by The Beatles END { $you->take($love) eq $you->made($love) ; }	[reply] [d/l] [select]
Re: making arrays that act like hashes at runtime by Sifmole (Chaplain) on Jul 01, 2002 at 11:28 UTC
This sounds alot like something called "psuedohashes". I believe Damian Conway's book "Object Oriented Perl" has a very good example of their use and information about them. Where are we linking to for books, now that FatBrain has been swallowed by B&N?	[reply]
Re^2: making arrays that act like hashes at runtime by particle (Vicar) on Jul 01, 2002 at 11:50 UTC
pseudo-hashes are experimental in perl 5. i haven't read any news about their continued existance in perl 6. in fact, i think they're disappearing in perl 5.10. thedamian's book, "Object Oriented Perl" can be linked to same as it ever was. simple searches for 'pseudohash' and 'pseudo-hash' reveal the following: using pseudo-hashes for unique lists (was Re: Re: Return a Unique Array) Whither the pseudohash? Using pseudohash for argument list validation and here is an off-site link to japhy's homepage http://www.crusoe.net/~jeffp/ where he has a tutorial on using pseudo-hashes. ~Particle accelerates	[reply] [d/l]

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