RE: Hash of arrays
Daniel Gross wrote, on Thursday, April 03, 2003 08:45
: > push @{$dirHash{$prefix}}, $item;
: Seems to work. It doesn't generate a syntax error. So, value elements
: within a hash are always references?
:
: BTW, in your opinion would this also work when $dirHash{$prefix} is
: undefined (i.e. when no key was defined yet?)
Ought to. I think I've done it, but I can't remember for sure. If it
doesn't, you can always test:
if ($dirHash{$prefix}) {
push ... ## as above
} else {
$dirHash{$prefix} = [$item]; # create the arrayref
}
Good luck,
Joe
==
Joseph P. Discenza, Sr. Programmer/Analyst
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Re: Hash of arrays
Daniel Gross wrote:
> Seems to work. It doesn't generate a syntax error. So, value elements
> within a hash are always references?
no, but they are always scalars :)
> BTW, in your opinion would this also work when $dirHash{$prefix} is
> undefined (i.e. when no key was defined yet?)
perl has a feature called autovivification, that usually Does The
Right Thing to create whatever you are trying to create.
Here is a tested full example from your original post:
#!/usr/bin/perl
use strict;
use warnings;
my @dirArray = qw(
abcdStuff1
acdeStuff1
abcdStuff2
Stuff2
acdeStuff2
Stuff1
);
my %dirHash = ();
foreach my $item(@dirArray) {
my $prefix = substr($item, 0,4);
push @{$dirHash{$prefix}}, $item;
}
use Data::Dumper;
print Data::Dumper->Dump([EMAIL PROTECTED], \%dirHash], [qw(*dirArray
*dirHash)]);
--
Alan F. Dickey - Interaction and Realization
http://www.intac.com/~afdickey
mailto:[EMAIL PROTECTED]
VOX: 908-273-3232 Cell: 908-334-0932
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RE: Hash of arrays
Thanks,
Seems to work. It doesn't generate a syntax error. So, value elements
within a hash are always references?
BTW, in your opinion would this also work when $dirHash{$prefix} is
undefined (i.e. when no key was defined yet?)
Thanks
Daniel
-Original Message-
From: Joseph P. Discenza [mailto:[EMAIL PROTECTED]
Sent: Thursday, April 03, 2003 8:36 AM
To: Daniel Gross; [EMAIL PROTECTED]
Subject: RE: Hash of arrays
Daniel Gross wrote, on Thursday, April 03, 2003 08:34
: I running into problems again: This time I'd like to fill a hash with
: arrays, however, the following push command generates a syntax error.
: Any idea why
:
: My %dirHash = ();
:
: foreach my $item(@dirArray) {
: $prefix = substr($item, 0,4);
: push @dirHash{$prefix}, $item;
: }
Try this (untested):
push @{$dirHash{$prefix}}, $item;
Remember, it's a hash of array *references*; you have to de-reference
the scalar that's in the hash in order to act on it as an array.
Joe
==
Joseph P. Discenza, Sr. Programmer/Analyst
mailto:[EMAIL PROTECTED]
Carleton Inc. http://www.carletoninc.com
574.243.6040 ext. 300fax: 574.243.6060
Providing Financial Solutions and Compliance for over 30 Years
* Please note that our Area Code has changed to 574! *
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Re: Hash of arrays
"Daniel Gross" <[EMAIL PROTECTED]> writes:
> I running into problems again: This time I'd like to fill a hash
> with arrays, however, the following push command generates a
> syntax error. Any idea why
> My %dirHash = ();
> foreach my $item(@dirArray) {
> $prefix = substr($item, 0,4);
> push @dirHash{$prefix}, $item;
> }
You can't push onto a hash. The syntax @dirHash{$prefix} is a hash slice.
Q.E.D.
I'm not quite sure what you're trying to do. Is it that you may have
multiple items per prefix, and you want them all in the same hash element?
If so, what you want is more like the following. Caution - cold code
follows:
foreach my $item (@dirArray) {
$prefix = substr ($item, 0, 4);
push @{$dirHash{$prefix}}, $item;
}
Tom Wyant
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RE: Hash of arrays
Daniel Gross wrote, on Thursday, April 03, 2003 08:34
: I running into problems again: This time I'd like to fill a hash with
: arrays, however, the following push command generates a syntax error.
: Any idea why
:
: My %dirHash = ();
:
: foreach my $item(@dirArray) {
: $prefix = substr($item, 0,4);
: push @dirHash{$prefix}, $item;
: }
Try this (untested):
push @{$dirHash{$prefix}}, $item;
Remember, it's a hash of array *references*; you have to de-reference
the scalar that's in the hash in order to act on it as an array.
Joe
==
Joseph P. Discenza, Sr. Programmer/Analyst
mailto:[EMAIL PROTECTED]
Carleton Inc. http://www.carletoninc.com
574.243.6040 ext. 300fax: 574.243.6060
Providing Financial Solutions and Compliance for over 30 Years
* Please note that our Area Code has changed to 574! *
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Hash of arrays
Hello all,
I running into problems again: This time I'd like to fill a hash with
arrays, however, the following push command generates a syntax error.
Any idea why
My %dirHash = ();
foreach my $item(@dirArray) {
$prefix = substr($item, 0,4);
push @dirHash{$prefix}, $item;
}
Thanks
Daniel
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creating array reference to one array of a hash of arrays
# I have a program that gets a hash from an API call.
# the format of the hash is that each key corresponds to an
# array. The following code snippet illustrates the data:
$href->{One} = [1,2,3,4];
print ref($href)."\n";
print ref($href->{One})."\n";
# I would like to simplify the syntax to use a simple array
# format by creating a new reference to the array to allow me
# to use the conventional syntax ie: $aref[0]
$aref = \@{$href->{One}};
print "$href->{One}=$aref\n";
# the output indicates that it did this...
# but this next line does not give the expected results
print "$href->{One}[0]=$aref[0]\n";
print "$href->{One}[0]=$aref->[0]\n";
#1. can I create a reference to this array that will allow me to
# access it without the -> operator?
#2. is there a simple explanation why I still need the -> operator?
#Howard Jares
#University of Houston
#Due to the current budget constraints, the light at the end of the tunnel
will be turned off until further notice.
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Re: hash of arrays
- Original Message -
From: "Peter Eisengrein" <[EMAIL PROTECTED]>
> That just adds a field to my output, like so:
>
> 7943641|ARRAY(0x1b9efb8)||
>
>
> Perhaps I'm contructing it wrong? I'm doing it like this...
>
> @_=$features{$dn};
> push(@_,$line[1]);
> $features{$dn}=\@_;
>
That's kind of scary, first you're saying the key in %features has an array
as content, then you're saying it has an array ref.
It's likely you had an array ref, pulled back an array with one entry (an
array ref) and then referenced back to that in the %features hash, avoiding
doing that will make life less complicated.
Look at something like this :
my %features = ();
foreach (1..10) {
my @array = (1,2,3);
$features{$_} = \@array;
}
foreach my $dn (sort {$a <=> $b} keys(%features)) {
print("\n$dn | ");
push(@{ $features{$dn} },"testline");
foreach (0..$#{ $features{$dn} }) {
my $dat = $features{$dn}->[$_];
print("$dat |");
}
}
!c
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RE: hash of arrays
BINGO! Thanks Rob.
> -Original Message-
> From: Hanson, Robert [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, January 16, 2002 10:58
> To: 'Peter Eisengrein'
> Subject: RE: hash of arrays
>
>
> Hmmm...
>
> If $features{$dn} is a reference to an array you dereference
> it like this...
>
> @{$features{$dn}}
>
> And you can also push onto it like this...
>
> push @{$features{$dn}}, 'foo';
>
> So I would rewrite the code to sent to look like this...
>
> push(@{$features{$dn}},$line[1]);
>
> Rob
>
>
> -Original Message-
> From: Peter Eisengrein [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, January 16, 2002 10:45 AM
> To: Hanson, Robert; Perl-Win32-Users Mailing List (E-mail)
> Subject: RE: hash of arrays
>
>
> That just adds a field to my output, like so:
>
> 7943641|ARRAY(0x1b9efb8)||
>
>
> Perhaps I'm contructing it wrong? I'm doing it like this...
>
> @_=$features{$dn};
> push(@_,$line[1]);
> $features{$dn}=\@_;
>
>
>
>
> > -Original Message-
> > From: Hanson, Robert [mailto:[EMAIL PROTECTED]]
> > Sent: Wednesday, January 16, 2002 10:43
> > To: 'Peter Eisengrein'; Perl-Win32-Users Mailing List (E-mail)
> > Subject: RE: hash of arrays
> >
> >
> >
> > This is what you want...
> >
> > foreach my $dn (keys %features)
> > {
> > my @features = @{$features{$dn}};
> >
> > print "$dn|";
> > foreach (@features)
> > {
> > print "$_\|";
> > }
> > print "\n";
> > }
> >
> > Rob
> >
> >
> > -Original Message-----
> > From: Peter Eisengrein [mailto:[EMAIL PROTECTED]]
> > Sent: Wednesday, January 16, 2002 10:33 AM
> > To: Perl-Win32-Users Mailing List (E-mail)
> > Subject: hash of arrays
> >
> >
> > I know this has been asked and answered so please forgive me,
> > but I left my
> > camel at home and can't seem to find it with perldoc...
> >
> > I have constructed a hash of arrays in %features but can't
> > get the data
> > back. I'm trying:
> >
> > #
> > foreach my $dn (keys %features)
> > {
> > my @features=$features{$dn};
> >
> > print "$dn|";
> > foreach (@features)
> > {
> > print "$_\|";
> > }
> > print "\n";
> > }
> > #
> >
> > but I get something like:
> >
> > 8204932|ARRAY(0x1b9efb8)|
> >
> >
> > How do I dereference it?
> >
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> >
>
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RE: hash of arrays
That just adds a field to my output, like so:
7943641|ARRAY(0x1b9efb8)||
Perhaps I'm contructing it wrong? I'm doing it like this...
@_=$features{$dn};
push(@_,$line[1]);
$features{$dn}=\@_;
> -Original Message-
> From: Hanson, Robert [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, January 16, 2002 10:43
> To: 'Peter Eisengrein'; Perl-Win32-Users Mailing List (E-mail)
> Subject: RE: hash of arrays
>
>
>
> This is what you want...
>
> foreach my $dn (keys %features)
> {
> my @features = @{$features{$dn}};
>
> print "$dn|";
> foreach (@features)
> {
> print "$_\|";
> }
> print "\n";
> }
>
> Rob
>
>
> -Original Message-
> From: Peter Eisengrein [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, January 16, 2002 10:33 AM
> To: Perl-Win32-Users Mailing List (E-mail)
> Subject: hash of arrays
>
>
> I know this has been asked and answered so please forgive me,
> but I left my
> camel at home and can't seem to find it with perldoc...
>
> I have constructed a hash of arrays in %features but can't
> get the data
> back. I'm trying:
>
> #
> foreach my $dn (keys %features)
> {
> my @features=$features{$dn};
>
> print "$dn|";
> foreach (@features)
> {
> print "$_\|";
> }
> print "\n";
> }
> #
>
> but I get something like:
>
> 8204932|ARRAY(0x1b9efb8)|
>
>
> How do I dereference it?
>
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>
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