Newbee Questions - Hash of Hashes / data structures

[cptk]

24 hours into my 1st Perl coding, and I'm jumping right into data structures. I'm testing conceptual stuff 1st.I have some questions:

1.) is the line "my %byaid" defined correctly?
2.) where I use "undef"'s, is this right?
3.) why am I not getting what I expect in the output?

Please go easy on me ... thanks!


#! /usr/perl5/5.6.1/bin/perl -w
use strict;
#use Class::Struct;

my %byaid;

my $rec = {
AID => undef,
STATUS => undef,
};

$rec->{AID} = "A";
$rec->{STATUS} = "stat-A";
$byaid{ $rec->{AID} } = $rec;

$rec->{AID} = "B";
$rec->{STATUS} = "stat-B";
$byaid{ $rec->{AID} } = $rec;

$rec->{AID} = "C";
$rec->{STATUS} = "stat-C";
$byaid{ $rec->{AID} } = $rec;

foreach my $x (keys %byaid) {
print "byaid key= ".$x."\n";
printf "AID=%s STATUS=%s\n",
$byaid{$x}{AID},
$byaid{$x}{STATUS};
}


OUTPUT:
byaid key= A
AID=C STATUS=stat-C
byaid key= B
AID=C STATUS=stat-C
byaid key= C
AID=C STATUS=stat-C

I was expecting:
byaid key= A
AID=A STATUS=stat-A
byaid key= B
AID=B STATUS=stat-B
byaid key= C
AID=C STATUS=stat-C

 

[cptk]

ahhhh,

I need to add $rec={}; before assigning additional values.
Like malloc in C ....

$rec={};
$rec->{AID} = "B";
$rec->{STATUS} = "stat-B";
$byaid{ $rec->{AID} } = $rec;

$rec={};
$rec->{AID} = "C";
$rec->{STATUS} = "stat-C";
$byaid{ $rec->{AID} } = $rec;

 

[PinkeyNBrain]

Not sure what you're goal is, but try

%{$byaid{ $rec->{AID} }} = %{$rec};

If this is you're first prog, you may want to slow down or you're going to hurt yourself

 

[KevinADC]

1.) is the line "my %byaid" defined correctly?
2.) where I use "undef"'s, is this right?
3.) why am I not getting what I expect in the output?

1. Yes. But all it does is declare the variable for later use.

2. Using undef is almost never necessary as the valu eof a variable. You can also define the value as an empty string '' or a 0 (zero) if you want it to have an initial false value.

3. There is no way to answer that because nobody knows what you expect the output to be.

------------------------------------------
- Kevin, perl coder unexceptional!

 

[cptk]

I'm creating a hash of hashes, where AID is the key of the outer hash (outer has is "byaid"). I was simply consectively pumping data to the "rec" hash structure, and then assigning that structure to the outer byaid hash. I was expecting (as orig. stated) the following:

byaid key= A
AID=A STATUS=stat-A
byaid key= B
AID=B STATUS=stat-B
byaid key= C
AID=C STATUS=stat-C

Instead I was getting the same values for all three records.
Declaring a new memory space for each record does the trick - I'll also try Pinkey's idea:
%{$byaid{ $rec->{AID} }} = %{$rec};

Thanks!

...and no, this is not my 1st program, just my 1st exposure to perl ...

 

[PinkeyNBrain]

Not sure what you're goal is, but try

%{$byaid{ $rec->{AID} }} = %{$rec};

If this is you're first prog, you may want to slow down or you're going to hurt yourself

 

[PinkeyNBrain]

??? Just looking back on some posts - my browser, Firefox, just indicated it had to resend something - next thing I know my post from last Friday is in here again ... I'd say oops or sorry if I knew what happened.