An array of arrays

Could anybody help me out here?  Here's the message I just got from a guy I
know:

-----------
I was wondering if you know how to create and access an array of arrays in
Perl. Basically I'm parsing an exported text file containing e-mails and I
think I want to move some fields into arrays until I'm ready to do my
report. Here basically is what I'm looking at doing:


^
|
|
Array 1
(messages)
|
|
v
<------ Array 2 ------->
(message fields:FROM, TO, CC, etc, sensitivity, etc)

I want to be able to search through the first array to count how many
messages are from a certain division, to a certain division and the message
sensitivity and then generate a report based on this info.

Any ideas?
------------

Like he said...any ideas?

I'm not exactly sure what the best way is.



0
tmay
8/7/2002 4:49:39 AM
perl.beginners 29352 articles. 3 followers. Follow

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References or 'man perlref' is the short answer.  References create
arrays that point to other arrays in memory.  You can also create arrays
of hashes, hashes of arrays, and hashes of hashes.  References are an
important part of Perl.  I would recommend reading the man page then
asking some more specific questions after that.  References can get kind
of confusing first time around.

Hope this helps,

On Tue, 2002-08-06 at 23:49, Troy May wrote:
> Could anybody help me out here?  Here's the message I just got from a guy I
> know:
> 
> -----------
> I was wondering if you know how to create and access an array of arrays in
> Perl. Basically I'm parsing an exported text file containing e-mails and I
> think I want to move some fields into arrays until I'm ready to do my
> report. Here basically is what I'm looking at doing:
> 
> 
> ^
> |
> |
> Array 1
> (messages)
> |
> |
> v
> <------ Array 2 ------->
> (message fields:FROM, TO, CC, etc, sensitivity, etc)
> 
> I want to be able to search through the first array to count how many
> messages are from a certain division, to a certain division and the message
> sensitivity and then generate a report based on this info.
> 
> Any ideas?
> ------------
> 
> Like he said...any ideas?
> 
> I'm not exactly sure what the best way is.
> 
> 
> 
> 
> -- 
> To unsubscribe, e-mail: beginners-unsubscribe@perl.org
> For additional commands, e-mail: beginners-help@perl.org
> 
-- 
Bryan DeLuca
UNIX guy

Public key available at:  ftp://ftp.supakewl.com/pub/bryan_pub.key
This E-mail was scanned by Carnivore.  Get GNUpg http://www.gnupg.org

0
bryan
8/7/2002 4:46:02 AM
Straight from the docs...

<perldsc>
ARRAYS OF ARRAYS
  Declaration of a ARRAY OF ARRAYS

     @AoA = (
            [ "fred", "barney" ],
            [ "george", "jane", "elroy" ],
            [ "homer", "marge", "bart" ],
          );

  Generation of a ARRAY OF ARRAYS

     # reading from file
     while ( <> ) {
         push @AoA, [ split ];
     }

     # calling a function
     for $i ( 1 .. 10 ) {
         $AoA[$i] = [ somefunc($i) ];
     }

     # using temp vars
     for $i ( 1 .. 10 ) {
         @tmp = somefunc($i);
         $AoA[$i] = [ @tmp ];
     }

     # add to an existing row
     push @{ $AoA[0] }, "wilma", "betty";

  Access and Printing of a ARRAY OF ARRAYS

     # one element
     $AoA[0][0] = "Fred";

     # another element
     $AoA[1][1] =~ s/(\w)/\u$1/;

     # print the whole thing with refs
     for $aref ( @AoA ) {
         print "\t [ @$aref ],\n";
     }

     # print the whole thing with indices
     for $i ( 0 .. $#AoA ) {
         print "\t [ @{$AoA[$i]} ],\n";
     }

     # print the whole thing one at a time
     for $i ( 0 .. $#AoA ) {
         for $j ( 0 .. $#{ $AoA[$i] } ) {
             print "elt $i $j is $AoA[$i][$j]\n";
         }
     }
</perldsc>

> -----Original Message-----
> From: Troy May [mailto:tmay@sierrasoho.org]
> Sent: Wednesday, August 07, 2002 2:50 PM
> To: Perl Beginners
> Subject: An array of arrays
> 
> 
> Could anybody help me out here?  Here's the message I just 
> got from a guy I
> know:
> 
> -----------
> I was wondering if you know how to create and access an array 
> of arrays in
> Perl. Basically I'm parsing an exported text file containing 
> e-mails and I
> think I want to move some fields into arrays until I'm ready to do my
> report. Here basically is what I'm looking at doing:
> 
> 
> ^
> |
> |
> Array 1
> (messages)
> |
> |
> v
> <------ Array 2 ------->
> (message fields:FROM, TO, CC, etc, sensitivity, etc)
> 
> I want to be able to search through the first array to count how many
> messages are from a certain division, to a certain division 
> and the message
> sensitivity and then generate a report based on this info.
> 
> Any ideas?
> ------------
> 
> Like he said...any ideas?
> 
> I'm not exactly sure what the best way is.
> 
> 
> 
> 
> -- 
> To unsubscribe, e-mail: beginners-unsubscribe@perl.org
> For additional commands, e-mail: beginners-help@perl.org
> 
0
toby
8/7/2002 4:58:10 AM
[...]
> I was wondering if you know how to create and access an array of arrays in
> Perl. 

@A = qw (1 2 3 4 5);
@B = qw (A B C D E);
@C = (\@A, \@B);

$C[1][0] is A
$C[0][4] is 5

# I will treat this \ as the Dimension Z, since
# X is -- , and Y is | 

Another style :

@A = ( qw [1 2 3 4 5], qw [A B C D E]);
$A[1][0] is A
$A[0][4] is 5


> Basically I'm parsing an exported text file containing e-mails and I
> think I want to move some fields into arrays until I'm ready to do my
> report. Here basically is what I'm looking at doing:
> 
> 
> ^
> |
> |
> Array 1
> (messages)
> |
> |
> v
> <------ Array 2 ------->
> (message fields:FROM, TO, CC, etc, sensitivity, etc)
> 
> I want to be able to search through the first array to count how many
> messages are from a certain division, 

What is the "certain division" ? Do you mean DimX ? or DimY ? or DimZ ?
I don't really understand, but anyway, I think you better try to use
AoH, which will looks like :

$mesg[0]{NAME} = 'PETER';
$mesg[0]{EMAIL}= 'PETER@HISPLACE.COM';
$mesg[0]{TO}   = 'SOME@OTPLACE.COM';

to create this, you can do it by :

open FH, "yourfile";
my @mesg = ();
while (my $row = <YOUR_FH>)
{ my @data = split /\t/, $row; # \t is just for example.
    my %COLS = (NAME => $data[0], EMAIL => $data[1], TO => $data[2] ) ;
    push @mesg, \%COLS;
}
close FH;


Rgds,
Connie



0
unknown
8/7/2002 5:21:56 AM
> -----Original Message-----
> From: Troy May [mailto:tmay@sierrasoho.org]
> Sent: Wednesday, August 07, 2002 12:50 AM
> To: Perl Beginners
> Subject: An array of arrays
> 
> 
> Could anybody help me out here?  Here's the message I just 
> got from a guy I
> know:
> 
> -----------
> I was wondering if you know how to create and access an array 
> of arrays in
> Perl. Basically I'm parsing an exported text file containing 
> e-mails and I
> think I want to move some fields into arrays until I'm ready to do my
> report. Here basically is what I'm looking at doing:
> 
> 
> ^
> |
> |
> Array 1
> (messages)
> |
> |
> v
> <------ Array 2 ------->
> (message fields:FROM, TO, CC, etc, sensitivity, etc)
> 
> I want to be able to search through the first array to count how many
> messages are from a certain division, to a certain division 
> and the message
> sensitivity and then generate a report based on this info.

Others have ably answered how to create arrays of arrays.

But based on the description of the problem, I'm not sure that's
necessarily the best approach. If you want to do counts by
sensitivity, from address, to address, etc., then sucking the
whole file into a huge memory structure isn't going to help
all that much. Why not just read through the file and accumulate
the counts you're interested in as you go? Or is there some
unspoken reason why an array of arrays is the way to go here?

This might be a case of an "XY" question. 
cf. http://perl.plover.com/Questions3.html
0
Bob_Showalter
8/7/2002 12:59:06 PM
I agree with Bob. dumping possibly large files to memory is generally not a
good idea.
I would say use a hash of hashs or array of hashs to store some of the
information from the e-mail and possibly store the position in the file of
the e-mail and it's length. Then at a later point in your program you can
seek to the position and read the bytes for e-mail content. (This will only
work if the file is not modified and only appended to during the time your
program is running).

or you could just flip throught the file searching for some unique
identifier for the e-mail that you store to your data structure.

array of arrays tutorial:
perldoc perllol

> -----Original Message-----
> From: Bob Showalter [mailto:Bob_Showalter@taylorwhite.com]
> Sent: Wednesday, August 07, 2002 8:59 AM
> To: 'Troy May'; Perl Beginners
> Subject: RE: An array of arrays
> 
> 
> > -----Original Message-----
> > From: Troy May [mailto:tmay@sierrasoho.org]
> > Sent: Wednesday, August 07, 2002 12:50 AM
> > To: Perl Beginners
> > Subject: An array of arrays
> > 
> > 
> > Could anybody help me out here?  Here's the message I just 
> > got from a guy I
> > know:
> > 
> > -----------
> > I was wondering if you know how to create and access an array 
> > of arrays in
> > Perl. Basically I'm parsing an exported text file containing 
> > e-mails and I
> > think I want to move some fields into arrays until I'm 
> ready to do my
> > report. Here basically is what I'm looking at doing:
> > 
> > 
> > ^
> > |
> > |
> > Array 1
> > (messages)
> > |
> > |
> > v
> > <------ Array 2 ------->
> > (message fields:FROM, TO, CC, etc, sensitivity, etc)
> > 
> > I want to be able to search through the first array to 
> count how many
> > messages are from a certain division, to a certain division 
> > and the message
> > sensitivity and then generate a report based on this info.
> 
> Others have ably answered how to create arrays of arrays.
> 
> But based on the description of the problem, I'm not sure that's
> necessarily the best approach. If you want to do counts by
> sensitivity, from address, to address, etc., then sucking the
> whole file into a huge memory structure isn't going to help
> all that much. Why not just read through the file and accumulate
> the counts you're interested in as you go? Or is there some
> unspoken reason why an array of arrays is the way to go here?
> 
> This might be a case of an "XY" question. 
> cf. http://perl.plover.com/Questions3.html
> 
> -- 
> To unsubscribe, e-mail: beginners-unsubscribe@perl.org
> For additional commands, e-mail: beginners-help@perl.org
> 

----------------------------------------------------------------------------
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The views and opinions expressed in this email message are the sender's
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Systems Inc.

0
nikola_janceski
8/7/2002 1:09:37 PM
"Connie Chan" <unknown@reborn.org> writes:

> [...]
> > I was wondering if you know how to create and access an array of arrays in
> > Perl. 
> 
> @A = qw (1 2 3 4 5);
> @B = qw (A B C D E);
> @C = (\@A, \@B);
> 
> $C[1][0] is A
> $C[0][4] is 5
> 
> # I will treat this \ as the Dimension Z, since
> # X is -- , and Y is | 
> 
> Another style :
> 
> @A = ( qw [1 2 3 4 5], qw [A B C D E]);
> $A[1][0] is A
> $A[0][4] is 5


I think you mean:

@A = ( [qw/1 2 3 4 5/], [qw/A B C D E/]);

-RN

-- 

Robin Norwood
Red Hat, Inc.

"The Sage does nothing, yet nothing remains undone."
-Lao Tzu, Te Tao Ching
0
rnorwood
8/7/2002 1:36:43 PM
On Wed, Aug 07, 2002 at 01:21:56PM +0800, Connie Chan wrote:
> 
> @A = qw (1 2 3 4 5);
> @B = qw (A B C D E);
> @C = (\@A, \@B);

>$C[1][0] is A
>$C[0][4] is 5

Darn! I didn't relize you could assign to a referenced array in this
way. I thought you had to derefernce them first. Boy, if I had known
that, I could have saved a few lines of code!

Incidently, how to you get a value from a reference array that looks
like this:

@A = qw(a b c d);
@B = qw(1 2 3);
@C = (\@A, \@B);

print $C[2][2];

ERROR! Since the value is out of range, and since @C is a referenced
array, perl gives you an error message. I want to say something like "If
array C has a value in index 2, then print." I have been determing the
size of the array in order to do this:

my $size = @C;
if ($size >1){
	$ref = $C[2]
	@temp = @{$ref};
	print $temp[2];
}


-- 

************************
*Paul Tremblay         *
*phthenry@earthlink.net*
************************
0
phthenry
8/7/2002 7:07:19 PM
see inline comments:

> -----Original Message-----
> From: Paul Tremblay [mailto:phthenry@earthlink.net]
> Sent: Wednesday, August 07, 2002 3:07 PM
> To: Perl Beginners
> Subject: Re: An array of arrays
> 
> 
> On Wed, Aug 07, 2002 at 01:21:56PM +0800, Connie Chan wrote:
> > 
> > @A = qw (1 2 3 4 5);
> > @B = qw (A B C D E);
> > @C = (\@A, \@B);
> 
> >$C[1][0] is A
> >$C[0][4] is 5
> 
> Darn! I didn't relize you could assign to a referenced array in this
> way. I thought you had to derefernce them first. Boy, if I had known
> that, I could have saved a few lines of code!
> 
> Incidently, how to you get a value from a reference array that looks
> like this:
> 
> @A = qw(a b c d);
> @B = qw(1 2 3);
> @C = (\@A, \@B);
> 
> print $C[2][2];
> 
> ERROR! Since the value is out of range, and since @C is a referenced
> array, perl gives you an error message. I want to say 
> something like "If
> array C has a value in index 2, then print." I have been determing the
> size of the array in order to do this:

in perl 5.6.1 there is a function called exists()
which tests if the range exists in the first place.
so for above
print $C[2][2] if exists $C[2] && exists $C[2][2];

## dunno if you can just use the last test but try it.

> 
> my $size = @C;
> if ($size >1){
> 	$ref = $C[2]
> 	@temp = @{$ref};
> 	print $temp[2];
> }
> 
> 
> -- 
> 
> ************************
> *Paul Tremblay         *
> *phthenry@earthlink.net*
> ************************
> 
> -- 
> To unsubscribe, e-mail: beginners-unsubscribe@perl.org
> For additional commands, e-mail: beginners-help@perl.org
> 

----------------------------------------------------------------------------
--------------------
The views and opinions expressed in this email message are the sender's
own, and do not necessarily represent the views and opinions of Summit
Systems Inc.

0
nikola_janceski
8/7/2002 7:12:41 PM
> > 
> > @A = qw (1 2 3 4 5);
> > @B = qw (A B C D E);
> > @C = (\@A, \@B);
> 
> >$C[1][0] is A
> >$C[0][4] is 5
> 
> Darn! I didn't relize you could assign to a referenced array in this
> way. 

Why not ?

> I thought you had to derefernce them first. Boy, if I had known
> that, I could have saved a few lines of code!

So seems you had writtern few more lines of code now ;)
By the way, I am not Boy =)

> Incidently, how to you get a value from a reference array that looks
> like this:
> 
> @A = qw(a b c d);
> @B = qw(1 2 3);
> @C = (\@A, \@B);
> 
> print $C[2][2];

So I got nothing. (null or undefined)when "use warnings" is not 
turned on. Besides, that's not a assign method's problem, but the 
the problem of how do you get the value.

> ERROR! Since the value is out of range, and since @C is a referenced
> array, perl gives you an error message. 

So you mean "use warnings" ? Okay, so how about this :
$C[10][10] = '' unless defined $C[10][10] ;
print $C[10][10] # have no problem.

As in the OP's case, the approach there is a fixed X Dimension. and
can get Y dim by $#arr to count from 0 or scalar(@arr) to count from 1.
So just use a simple loop to roll over the AoA and to fill up the 'holes'.


> I want to say something like "If array C has a value in index 2, then 
> print." I have been determing the size of the array in order to do this:
> 
> my $size = @C;
> if ($size >1){
> $ref = $C[2]
> @temp = @{$ref};
> print $temp[2];
> }

There's another more effective way beside of unless defined, 
see, perldoc -f exists()


Rgds,
Connie


0
unknown
8/8/2002 4:01:17 AM
Reply:

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Who's on the bookshelves this month? Dogs, wolves, birds and cats. And butterflies. Beautiful butterflies. Here are some of the new animal-related ...

Violin All-Flash Arrays Aimed at High-end, Starter Markets
Take your pick: 140TB of raw flash in three-rack units, with 1.1 million IOPS, or a not-quite-as-fast starter array for under $100,000.

Sheldon Silver, Longtime Titan of New York Politics, Guilty On Array of Corruption Charges
Sheldon Silver, who has been speaker of the New York State Assembly for 20 years, was found guilty today in federal court of seven corruption ...

Alien megastructures? SETI Institute’s Allen Telescope Array targets weirdly winking star
One of the premier telescope arrays in the search for extraterrestrial intelligence, or SETI, is focusing its antennas on an anomalously blinking ...

El Cheapo Phased-Array Sonar
... — the range to the closest object that the speaker is pointing at. It doesn’t have to be that way. [Graham Chow] built a simple phased-array ...

‘Geminid’ Meteor Shower: Scintillating Array Of ‘Shooting Stars’ To Illuminate December Night Sky
Stargazers across the world will witness a wondrous array of spectacular shooting stars illuminating the night sky this weekend. The mesmerizing ...

Sundance announces its 2016 lineup, offering an array of timely films
Over its 31 editions, the Sundance Film Festival has showcased timeless tales of people enduring heartbreak, coming of age, attempting violence ...

Resources last updated: 12/17/2015 1:11:58 AM