Re: Filehandle within foreach loop

[David Mertens]

Yes, and I think that gives us *two* reasons to always explicitly close
filehandles. :-)

David

On Sun, Jul 16, 2017 at 8:00 AM, Shawn H Corey 
wrote:

> On Sun, 16 Jul 2017 07:36:39 -0400
> David Mertens  wrote:
>
> > Also note that lexical filehandles close when they go out of scope
>
> True but you should always explicitly close your files. This gives you
> a chance to report any errors it had, have rather than silently
> ignoring them.
>
>
> --
> Don't stop where the ink does.
>
> Shawn H Corey
>
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>
>
>


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Re: Filehandle within foreach loop

[Shawn H Corey]

On Sun, 16 Jul 2017 07:36:39 -0400
David Mertens  wrote:

> Also note that lexical filehandles close when they go out of scope

True but you should always explicitly close your files. This gives you
a chance to report any errors it had, have rather than silently
ignoring them.


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Re: Filehandle within foreach loop

[David Mertens]

Even more readable:

FILE: foreach my $file ( @files ) }
  ...
  last FILE if (some_condition);
  ...
}

Also note that lexical filehandles close when they go out of scope, except
for the most recently "stat"ed file. Perl holds a reference to "the most
recently stat-ed filehandle" in "the solitary underscore" as discussed in the
documentation about -X <https://perldoc.perl.org/functions/-X.html>. The
upshot is that a filehandle used in an expression like "-M $fh" will live
until the next such expression, and the filehandle used in the last such
expression won't close until the end of the program.

David

On Wed, Jul 12, 2017 at 5:28 PM, Jim Gibson <jimsgib...@gmail.com> wrote:

> If you wish to terminate execution of a foreach loop without iterating
> over all of the elements (@files, in this case) use the “last” statement:
>
> foreach my $file ( @files ) {
>  # process file
>  open( my $fh, ‘<‘, $file ) or die(…);
>  while( my $line = <$fh> ) {
># process line
>  }
>  close ($fh) or die( … );
>
>  last if (some_condition);
> }
>
> If you wish to terminate the foreach loop from inside the while loop, you
> can give the foreach loop a label and use the label in the “last”
> statement. Without an explicit label, “last” will terminate the innermost
> loop (the while loop here):
>
> ALL: foreach my $file ( @files ) {
>  # process file
>  open( my $fh, ‘<‘, $file ) or die(…);
>  while( my $line = <$fh> ) {
># process line
>last ALL if (some_condition);
>  }
>  close ($fh) or die( … );
> }
>
> However, in that case you have skipped the close statement, and the close
> will happen automatically when the file handle $fh goes out of scope, but
> you cannot do any explicit error checking on the close.
>
>
> > On Jul 12, 2017, at 12:20 PM, perl kamal <kamal.p...@gmail.com> wrote:
> >
> > Hello All,
> >
> > I would like to read multiple files and process them.But we could read
> the first file alone and the rest are skipped from the while loop. Please
> correct me where am i missing the logic.Thanks.
> >
> > use strict;
> > use warnings;
> > my @files=qw(Alpha.txt Beta.txt Gama.txt);
> >
> > foreach my $file (@files)
> > {
> > open (my $FH, $file) or die "could not open file\n";
> >
> > while( my $line = <$FH> ){
> > #[process the lines & hash construction.]
> > }
> > close $FH;
> > }
> >
> > Regards,
> > Kamal.
>
>
>
> Jim Gibson
>
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>
>
>


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Re: Filehandle within foreach loop

[Shawn H Corey]

On Thu, 13 Jul 2017 00:50:42 +0530
perl kamal  wrote:

> open (my $FH, $file) or die "could not open file\n";

A quick note: output the file name and error message to have a better
idea of what went wrong.

open (my $FH, $file) or die "could not open file $file: $!\n";


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Re: Filehandle within foreach loop

[Jim Gibson]

If you wish to terminate execution of a foreach loop without iterating over all 
of the elements (@files, in this case) use the “last” statement:

foreach my $file ( @files ) {
 # process file
 open( my $fh, ‘<‘, $file ) or die(…);
 while( my $line = <$fh> ) {
   # process line
 }
 close ($fh) or die( … );

 last if (some_condition);
}

If you wish to terminate the foreach loop from inside the while loop, you can 
give the foreach loop a label and use the label in the “last” statement. 
Without an explicit label, “last” will terminate the innermost loop (the while 
loop here):

ALL: foreach my $file ( @files ) {
 # process file
 open( my $fh, ‘<‘, $file ) or die(…);
 while( my $line = <$fh> ) {
   # process line
   last ALL if (some_condition);
 }
 close ($fh) or die( … );
}

However, in that case you have skipped the close statement, and the close will 
happen automatically when the file handle $fh goes out of scope, but you cannot 
do any explicit error checking on the close.


> On Jul 12, 2017, at 12:20 PM, perl kamal <kamal.p...@gmail.com> wrote:
> 
> Hello All,
> 
> I would like to read multiple files and process them.But we could read the 
> first file alone and the rest are skipped from the while loop. Please correct 
> me where am i missing the logic.Thanks. 
> 
> use strict;
> use warnings;
> my @files=qw(Alpha.txt Beta.txt Gama.txt);
> 
> foreach my $file (@files)
> {
> open (my $FH, $file) or die "could not open file\n";
> 
> while( my $line = <$FH> ){
> #[process the lines & hash construction.]
> }
> close $FH;
> }
> 
> Regards,
> Kamal.



Jim Gibson

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Re: Filehandle within foreach loop

[Chas. Owens]

That code will read each line from each file.  The problem is likely in the
part that says:

#[process the lines & hash construction.]

What are you doing there?

On Wed, Jul 12, 2017 at 3:23 PM perl kamal <kamal.p...@gmail.com> wrote:

> Hello All,
>
> I would like to read multiple files and process them.But we could read the
> first file alone and the rest are skipped from the while loop. Please
> correct me where am i missing the logic.Thanks.
>
> use strict;
> use warnings;
> my @files=qw(Alpha.txt Beta.txt Gama.txt);
>
> foreach my $file (@files)
> {
> open (my $FH, $file) or die "could not open file\n";
>
> while( my $line = <$FH> ){
> #[process the lines & hash construction.]
> }
> close $FH;
> }
>
> Regards,
> Kamal.
>

Filehandle within foreach loop

[perl kamal]

Hello All,

I would like to read multiple files and process them.But we could read the
first file alone and the rest are skipped from the while loop. Please
correct me where am i missing the logic.Thanks.

use strict;
use warnings;
my @files=qw(Alpha.txt Beta.txt Gama.txt);

foreach my $file (@files)
{
open (my $FH, $file) or die "could not open file\n";

while( my $line = <$FH> ){
#[process the lines & hash construction.]
}
close $FH;
}

Regards,
Kamal.

Re: map vs foreach

[Andy Bach]

On Tue, Sep 30, 2014 at 6:19 PM, David Precious dav...@preshweb.co.uk
wrote:

 Like most things, TIMTOWTDI, but I believe Perl Best Practices [PBP]
 advises
 against using map in void context.


As PBP[1] is encoded in Perl::Critic
map and grep are intended to be pure functions, not mutators. If you want
to iterate with side-effects, then you should use a proper for or foreach
loop.

Somewhere there's a quote (possibly apocryphal but wait! [2]) from Larry
Wall on a map vs foreach thread:
That being said, I'd never grep someone in a void context myself.

He actually wasn't condemning the use of map/grep in a void context per se,
just noting his personal preference.

a

[1]
Perl Best Practices
 Standards and Styles for Developing Maintainable Code
By Damian Conway http://shop.oreilly.com/product/9780596001735.do#tab_04_2

http://shop.oreilly.com/product/9780596001735.do

[2]
quoted here:
http://www.perlmonks.org/?node_id=809543

Andy Bach,
afb...@gmail.com
608 658-1890 cell
608 261-5738 wk

map vs foreach

[SSC_perl]

Is the output of these two lines equivalent?

map { $hash-{$_} = shift @record } @{$self-{'FIELDNAMES'}};

$hash-{$_} = shift @record foreach @{$self-{'FIELDNAMES'}};

They appear to be in my testing, but I'd like to make sure.

Is one more appropriate than the other in a situation like this, or is 
it simply a styling difference?

Thanks,
Frank

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Re: map vs foreach

[Omega -1911]

Is asking a preference-based question appropriate for a beginners list
appropriate?

Question for you: Have you updated your software to have a more modern look
and feel or does it still resemble 1995?
I ask because, in your own words, you said or is it simply a styling
difference?.

Feedback for you: The look and feel of your software quickly helps any
potential shopper to return to Amazon.

Yes, I am top-posting. Why? Because top-posting annoys me as well as most
on this list,  but so does seeing your signature in each of your trivial
questions, SEO initiatives and marketing schemes

And, [ drum roll ] you're welcome.

On Tue, Sep 30, 2014 at 5:08 PM, SSC_perl p...@surfshopcart.com wrote:

 Is the output of these two lines equivalent?

 map { $hash-{$_} = shift @record } @{$self-{'FIELDNAMES'}};

 $hash-{$_} = shift @record foreach @{$self-{'FIELDNAMES'}};

 They appear to be in my testing, but I'd like to make sure.

 Is one more appropriate than the other in a situation like this,
 or is it simply a styling difference?

 Thanks,
 Frank

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Re: map vs foreach

[Shawn H Corey]

On Tue, 30 Sep 2014 14:08:14 -0700
SSC_perl p...@surfshopcart.com wrote:

   Is the output of these two lines equivalent?
 
 map { $hash-{$_} = shift @record } @{$self-{'FIELDNAMES'}};
 
 $hash-{$_} = shift @record foreach @{$self-{'FIELDNAMES'}};
 
   They appear to be in my testing, but I'd like to make sure.
 
   Is one more appropriate than the other in a situation like
 this, or is it simply a styling difference?

Fancy tricks are fine...if you understand them. But do yourself a
favour: code like you will have to read it after an all-night party
(some day, you will).

foreach my $field_name ( @{ $self-{FIELDNAMES} } ){
  $hash-{ $field_name } = shift @record;
}

In other words, keep is simple.


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Re: map vs foreach

[David Precious]

On Tue, 30 Sep 2014 14:08:14 -0700
SSC_perl p...@surfshopcart.com wrote:

   Is the output of these two lines equivalent?
 
 map { $hash-{$_} = shift @record } @{$self-{'FIELDNAMES'}};
 
 $hash-{$_} = shift @record foreach @{$self-{'FIELDNAMES'}};
[...]
   Is one more appropriate than the other in a situation like
 this, or is it simply a styling difference?

map is more suitable when using it to transform a list; it doesn't make
sense to use it as a flow-control statement where a for loop would be
more sane.

In other words, if you're not assigning or using the result of the map
call, you're using it wrong, and a for loop would be more readable
(and, in older perls at least, likely more efficient).

So, e.g.:

my %fields = map { $_ = shift @record } @{$self-{'FIELDNAMES'}};

... would make sense, because you're using map to produce the data you
want, rather than using it instead of a for loop.

Like most things, TIMTOWTDI, but I believe Perl Best Practices advises
against using map in void context.

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Re: map vs foreach

[SSC_perl]

On Sep 30, 2014, at 4:08 PM, Shawn H Corey wrote:
 code like you will have to read it after an all-night party
 (some day, you will).

Those days are over, but point taken! ;)

Thanks,
Frank

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Re: map vs foreach

[SSC_perl]

On Sep 30, 2014, at 4:19 PM, David Precious wrote:
 So, e.g.:
 
 my %fields = map { $_ = shift @record } @{$self-{'FIELDNAMES'}};
 
 ... would make sense, because you're using map to produce the data you
 want, rather than using it instead of a for loop.

Thanks, David.  That was an excellent explanation!

As usual, I stumbled across an old thread on PerlMonks after I posted 
my question. :\  It was a good read, however, and it's helped to clear up my 
understanding of map.  If anyone else is interested, it's here:

http://www.perlmonks.org/?node_id=296742

However, David's response was pretty much everything that was in the 
thread, but in a nutshell.

Frank

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Re: map vs foreach

[Uri Guttman]

On 09/30/2014 05:08 PM, SSC_perl wrote:

Is the output of these two lines equivalent?

map { $hash-{$_} = shift @record } @{$self-{'FIELDNAMES'}};

$hash-{$_} = shift @record foreach @{$self-{'FIELDNAMES'}};

They appear to be in my testing, but I'd like to make sure.

Is one more appropriate than the other in a situation like this, or is 
it simply a styling difference?




both do the exact same thing. the general rule is to use map only when 
you are generating a new list which is the output of map. your code is 
called using map in a void context. perl used to generate the list and 
then throw it out which is a waste. even with that inefficiency fixed, 
it is still considered by most a poor coding style. you are telling the 
reader that you are building a list but don't use it.


the foreach is better style yet some might not like the shift trick (i 
have used that one). but you just are assigning a list of values to a 
list of tokens in a hash. a slice is the best and fastest way to do that.


my %hash ;
@hash{ @{$self-{'FIELDNAMES'} } = @record ;

done!

if you are using DBI, you can get the row back as a hash reference and 
not need that code.


uri




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Re: map vs foreach

[Shawn H Corey]

On Tue, 30 Sep 2014 16:38:24 -0700
SSC_perl p...@surfshopcart.com wrote:

 On Sep 30, 2014, at 4:08 PM, Shawn H Corey wrote:
  code like you will have to read it after an all-night party
  (some day, you will).  
 
   Those days are over, but point taken! ;)

They're never over but they do get farther apart. ;)


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Re: foreach and next

[Vyacheslav]

My code

my %attr = (
PrintError = 0,
RaiseError = 0
);
my $dbh = DBI-connect($dsn, $user, $pass, \%attr);
unless ($dbh) {
next;
}
my $query = SHOW DATABASES;

I use
unless ($dbh) {
next;
} and this work fine.

Thanks


09.04.2012 01:22, Jim Gibson написал:

At 12:50 AM + 4/9/12, Vyacheslav wrote:

I enabled RaiserError, then script die.
...
my %attr = (
PrintError = 0,
RaiseError = 1
);


Use:

RaiseError = 0

instead so that your script will not raise an exception and die. Then 
check $dbh-err.





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Re: foreach and next

[Rob Dixon]

On 09/04/2012 14:24, Vyacheslav wrote:

My code

my %attr = (
PrintError = 0,
RaiseError = 0
);
my $dbh = DBI-connect($dsn, $user, $pass, \%attr);
unless ($dbh) {
next;
}
my $query = SHOW DATABASES;

I use
unless ($dbh) {
next;
} and this work fine.

Thanks


09.04.2012 01:22, Jim Gibson написал:

At 12:50 AM + 4/9/12, Vyacheslav wrote:

I enabled RaiserError, then script die.
...
my %attr = (
PrintError = 0,
RaiseError = 1
);


Use:

RaiseError = 0

instead so that your script will not raise an exception and die. Then
check $dbh-err.






Hi Vyacheslav

I suggest you use this instead

my $dbh = DBI-connect($dsn, $user, $pass) or do {
  warn Can't connect to database $db: $DBI::errstr\n;
  next;
};

so that your program shows which database connections have failed and
been skipped.

This is pretty much the same as your original code except that a failure
to connect causes a warning instead of a fatal 'die', and execution
skips to the next database source. Also the warning string shows the
name of the database instead of saying just Can't connect to the DB.

HTH,

Rob

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Re: foreach and next

[Binish A.R]

Enclose DBI operation inside eval
-

#!/usr/bin/perl

use strict;
use warnings;
use DBI;
use DBD::mysql;

foreach $db (hostdb($project)) {

eval {
        my $server = $db;
        my $dbname = information_schema;
        my $port = 3306;
        my $dsn = dbi:mysql:$dbname:$server:$port;
        my $user = user;
        my $pass = pass;

        my $dbh = DBI-connect($dsn, $user, $pass) or die Can't connect to the 
DB: $DBI::errstr\n;
        my $query = SHOW DATABASES;
        my $sth = $dbh-prepare($query);
        $sth-execute;
        my @dbs;
        while ( my $data = $sth-fetchrow_arrayref ) {
                push @dbs, $data-[0];
        }

        $dbh-disconnect;
}; 

if ($@) {
        print host $db - not ok;
} else {
        print host $db - ok;
}

 
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 From: Vyacheslav agapov.sl...@gmail.com
To: beginners@perl.org 
Sent: Sunday, April 8, 2012 11:42 AM
Subject: foreach and next
 
Hello all.
My english bad and i have a problem.

I am connected to databases in a cycle foreach and the script die, if one of 
database is not available.

#!/usr/bin/perl

use strict;
use warnings;
use DBI;
use DBD::mysql;

foreach $db (hostdb($project)) {

my $server = $db;
my $dbname = information_schema;
my $port = 3306;
my $dsn = dbi:mysql:$dbname:$server:$port;
my $user = user;
my $pass = pass;

my $dbh = DBI-connect($dsn, $user, $pass) or die Can't connect to the DB: 
$DBI::errstr\n;
my $query = SHOW DATABASES;
my $sth = $dbh-prepare($query);
$sth-execute;
my @dbs;
while ( my $data = $sth-fetchrow_arrayref ) {
        push @dbs, $data-[0];
}

print host $db - ok;
$dbh-disconnect;

My result

host db1 - ok
host db2 - ok
host db3 - ok
DBI connect('information_schema:db4:3306','user',...) failed: Can't connect to 
MySQL server on 'db4' (111) at ./dbcheck.pl line 53
and script die

How I can pass an error that the cycle has continued execute? I need
host db1 - ok
host db2 - ok
host db3 - ok
...
host db10 - ok

Can I use next operator in this situation?



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Re: foreach and next

[Shlomi Fish]

Hi Vyacheslav,

On Sun, 08 Apr 2012 06:12:53 +
Vyacheslav agapov.sl...@gmail.com wrote:

 Hello all.
 My english bad and i have a problem.
 
 I am connected to databases in a cycle foreach and the script die, if 
 one of database is not available.
 
 #!/usr/bin/perl
 
 use strict;
 use warnings;
 use DBI;
 use DBD::mysql;
 
 foreach $db (hostdb($project)) {
 
 my $server = $db;
 my $dbname = information_schema;
 my $port = 3306;
 my $dsn = dbi:mysql:$dbname:$server:$port;
 my $user = user;
 my $pass = pass;
 
 my $dbh = DBI-connect($dsn, $user, $pass) or die Can't connect to the 
 DB: $DBI::errstr\n;

Your problem is that you are invoking die ... which throws an exception. See:

https://www.socialtext.net/perl5/exception_handling

Since this exception is not caught (using eval { ... }) it terminates the
entire program. So what you should do instead is handle it gracefully (say
using next):

my $dbh = DBI-connect($dsn, $user, $pass);

if (!$dbh)
{
next DB_HOSTS_LOOP; # And label the loop appropriately.
}

Regards,

Shlomi Fish

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Re: foreach and next

[Vyacheslav]

Thanks all.

using eval helped me.

08.04.2012 09:43, Shlomi Fish пишет:

Hi Vyacheslav,

On Sun, 08 Apr 2012 06:12:53 +
Vyacheslavagapov.sl...@gmail.com  wrote:


Hello all.
My english bad and i have a problem.

I am connected to databases in a cycle foreach and the script die, if
one of database is not available.

#!/usr/bin/perl

use strict;
use warnings;
use DBI;
use DBD::mysql;

foreach $db (hostdb($project)) {

my $server = $db;
my $dbname = information_schema;
my $port = 3306;
my $dsn = dbi:mysql:$dbname:$server:$port;
my $user = user;
my $pass = pass;

my $dbh = DBI-connect($dsn, $user, $pass) or die Can't connect to the
DB: $DBI::errstr\n;

Your problem is that you are invoking die ... which throws an exception. See:

https://www.socialtext.net/perl5/exception_handling

Since this exception is not caught (using eval { ... }) it terminates the
entire program. So what you should do instead is handle it gracefully (say
using next):

my $dbh = DBI-connect($dsn, $user, $pass);

if (!$dbh)
{
next DB_HOSTS_LOOP; # And label the loop appropriately.
}

Regards,

Shlomi Fish



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Re: foreach and next

[Shlomi Fish]

Hi Vyacheslav,

On Sun, 08 Apr 2012 15:10:06 +
Vyacheslav agapov.sl...@gmail.com wrote:

 Thanks all.
 
 using eval helped me.
 

The problem with eval in Perl 5 is that it catches any and all thrown exceptions
. I.e: by default, it doesn't do Object-Oriented exceptions like Java, Ruby,
Python and other languages do, though this can be done to a large extent
using some CPAN modules. As a result, by using eval, you risk easily trapping
other more meaningful exceptions, which *should* cause your program to
terminate.

In your case, you're throwing an exception explicitly upon failure, so if you're
not interested in an exception getting thrown, you should just handle the
failure differently.

( I also recall seeing something about excessive exceptions throwing and
trapping being costly in CPU time, but this shouldn't make a difference in this
case. )   

Regards,

Shlomi Fish 

-- 
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Why I Love Perl - http://shlom.in/joy-of-perl

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Re: foreach and next

[Dr.Ruud]

On 2012-04-08 17:10, Vyacheslav wrote:


using eval helped me.


You should not use exceptions for normal code flow.

Read the DBI docs (perldoc DBI).
If a failed connection must be an exception, set RaiseError to true.
But if it isn't an exception, leave it false, and test $dbh-err (or the 
global $DBI::err).


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Re: foreach and next

[Vyacheslav]

I enabled RaiserError, then script die.
...
my %attr = (
PrintError = 0,
RaiseError = 1
);

my $dbh = DBI-connect($dsn, $user, $pass, \%attr); # or die Can't 
connect to the DB: $DBI::errstr\n;

my $query = SHOW DATABASES;
my $sth = $dbh-prepare($query) or die Can't prepare SQL statement: 
$DBI::errstr\n;;

$sth-execute;
my @dbs;
while ( my $data = $sth-fetchrow_arrayref ) {
push @dbs, $data-[0];
}
...
DBI connect('information_schema:db1:3306','test',...) failed: Can't 
connect to MySQL server on 'db1' (111) at ./dbcheck.pl line 72


I test with $dbh-err, but the script all the same die.

08.04.2012 18:40, Dr.Ruud пишет:

On 2012-04-08 17:10, Vyacheslav wrote:


using eval helped me.


You should not use exceptions for normal code flow.

Read the DBI docs (perldoc DBI).
If a failed connection must be an exception, set RaiseError to true.
But if it isn't an exception, leave it false, and test $dbh-err (or 
the global $DBI::err).




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Re: foreach and next

[Jim Gibson]

At 12:50 AM + 4/9/12, Vyacheslav wrote:

I enabled RaiserError, then script die.
...
my %attr = (
PrintError = 0,
RaiseError = 1
);


Use:

  RaiseError = 0

instead so that your script will not raise an exception and die. Then 
check $dbh-err.



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foreach and next

[Vyacheslav]

Hello all.
My english bad and i have a problem.

I am connected to databases in a cycle foreach and the script die, if 
one of database is not available.


#!/usr/bin/perl

use strict;
use warnings;
use DBI;
use DBD::mysql;

foreach $db (hostdb($project)) {

my $server = $db;
my $dbname = information_schema;
my $port = 3306;
my $dsn = dbi:mysql:$dbname:$server:$port;
my $user = user;
my $pass = pass;

my $dbh = DBI-connect($dsn, $user, $pass) or die Can't connect to the 
DB: $DBI::errstr\n;

my $query = SHOW DATABASES;
my $sth = $dbh-prepare($query);
$sth-execute;
my @dbs;
while ( my $data = $sth-fetchrow_arrayref ) {
push @dbs, $data-[0];
}

print host $db - ok;
$dbh-disconnect;

My result

host db1 - ok
host db2 - ok
host db3 - ok
DBI connect('information_schema:db4:3306','user',...) failed: Can't 
connect to MySQL server on 'db4' (111) at ./dbcheck.pl line 53

and script die

How I can pass an error that the cycle has continued execute? I need
host db1 - ok
host db2 - ok
host db3 - ok
...
host db10 - ok

Can I use next operator in this situation?



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Re: Can recursion eliminate nested foreach() loops?

[Dr.Ruud]

On 2012-02-27 03:52, Shawn H Corey wrote:


There is no simplify way of doing this.


perl -wle '
  my $s = {red,green,blue},{small,large},{light,dark};
  print for glob $s;
'

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Re: Can recursion eliminate nested foreach() loops?

[Paul Johnson]

On Sun, Feb 26, 2012 at 09:30:44PM -0500, Steve Bertrand wrote:
 I came across a question early this morning on a forum that
 intrigued me. I literally spent about five hours trying everything
 to solve it, but I couldn't.

Sometimes Perl is just a means to get at the corect tool:

my $attributes =
[
  { type = 'colors',  values = [qw/red green blue/]  },
  { type = 'sizes',   values = [qw/small large/] },
  { type = 'shades',  values = [qw/light dark/] },
];

local $ = ,;
say y/-/ /r for glob join -, map {@{$_-{values}}}, @$attributes;


red small light
red small dark
red large light
red large dark
green small light
green small dark
green large light
green large dark
blue small light
blue small dark
blue large light
blue large dark


or perhaps you like commas but dislike maintenance programmers:

my $attributes =
[
  { type = 'colors',  values = [qw/red green blue/]  },
  { type = 'sizes',   values = [qw/small large/] },
  { type = 'shades',  values = [qw/light dark/] },
];

$=,;say for(glob(qq{@{[map+qq{{@{$_-{values,@$attributes]}}))


red,small,light
red,small,dark
red,large,light
red,large,dark
green,small,light
green,small,dark
green,large,light
green,large,dark
blue,small,light
blue,small,dark
blue,large,light
blue,large,dark


The key here is using globbing.  See perldoc -f glob for the details.  Using
bsd_glob would clean up the (first) code a little.

 I know this isn't a beginner's question

None of the concepts in this code are particularly tricky, but there are
quite a few of them in a short piece of code.

Is there a way to simplify this within Perl?

I suppose the question of whether or not this is simplified comes down to
definitions.

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Can recursion eliminate nested foreach() loops?

[Steve Bertrand]

I came across a question early this morning on a forum that intrigued 
me. I literally spent about five hours trying everything to solve it, 
but I couldn't.


Every attempt at recursion, counting, numbering, hashing etc failed. Is 
there a way to use recursion to eliminate the repeated and 
pre-calculated calls to foreach as this OP is asking?


From ... .. ... is verbatim 'dms000'

...

I need to generate a list of combinations from a data structure such as:

my $attributes =
[
  { type = 'colors',  values = [qw/red green blue/]  },
  { type = 'sizes',   values = [qw/small large/] },
  { type = 'shades',  values = [qw/light dark/] },
];

It is easy enough when the number of types are known:

my @combos = ();
foreach my $a (@{$attributes-[0]-{values}}) {
  foreach my $b (@{$attributes-[1]-{values}}) {
foreach my $c (@{$attributes-[2]-{values}}) {
  push @combos, [$a, $b, $c];
}
  }
}

Which results in a list such as:
red small light
red small dark
red large light
red large dark
green small light
...

But how to do with arbitrary number of types? Obviously will need 
recursion but I can't figure it out. The only thing I could come up with 
was generating code like code2 as a string and eval()ing it...a poor 
solution.


...

I know this isn't a beginner's question, but I know there are geniuses 
here. Is there a way to simplify this within Perl?


Steve

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Re: Can recursion eliminate nested foreach() loops?

[Shawn H Corey]

On 12-02-26 09:30 PM, Steve Bertrand wrote:

I know this isn't a beginner's question, but I know there are geniuses
here. Is there a way to simplify this within Perl?


There is no simplify way of doing this. Separate off the first attribute 
and cross-product it with a recursive call to the rest. Like this:


#!/usr/bin/env perl

use strict;
use warnings;

my $attributes =
[
  { type = 'colors',  values = [qw/red green blue/]  },
  { type = 'sizes',   values = [qw/small large/] },
  { type = 'shades',  values = [qw/light dark/] },
];

sub combo {
  my @traits = @_;

  # nothing given, nothing returned
  return if @traits == 0;

  # return the last list
  if( @traits == 1 ){
return map { [ $_ ] } @{ $traits[0]{values} };
  }

  # get the combos for everything but the first one
  my @combos = combo( @traits[ 1 .. $#traits ] );

  # now combine them
  my @result = ();
  for my $first ( @{ $traits[0]{values} } ){
for my $rest ( @combos ){
  push @result, [ $first, @$rest ];
}
  }

  return @result;
}

my @list = combo( @$attributes );

for my $set ( @list ){
  print @$set\n;
}

__END__

--
Just my 0.0002 million dollars worth,
  Shawn

Programming is as much about organization and communication
as it is about coding.

It's Mutual Aid, not fierce competition, that's the dominate
force of evolution.  Of course, anyone who has worked in
open source already knows this.

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Re: Can recursion eliminate nested foreach() loops?

[Steve Bertrand]

On 2012-02-26 21:52, Shawn H Corey wrote:

On 12-02-26 09:30 PM, Steve Bertrand wrote:

I know this isn't a beginner's question, but I know there are geniuses
here. Is there a way to simplify this within Perl?


There is no simplify way of doing this. Separate off the first attribute
and cross-product it with a recursive call to the rest. Like this:

#!/usr/bin/env perl

use strict;
use warnings;

my $attributes =
[
{ type = 'colors', values = [qw/red green blue/] },
{ type = 'sizes', values = [qw/small large/] },
{ type = 'shades', values = [qw/light dark/] },
];

sub combo {
my @traits = @_;

# nothing given, nothing returned
return if @traits == 0;

# return the last list
if( @traits == 1 ){
return map { [ $_ ] } @{ $traits[0]{values} };
}

# get the combos for everything but the first one
my @combos = combo( @traits[ 1 .. $#traits ] );

# now combine them
my @result = ();
for my $first ( @{ $traits[0]{values} } ){
for my $rest ( @combos ){
push @result, [ $first, @$rest ];
}
}

return @result;
}

my @list = combo( @$attributes );

for my $set ( @list ){
print @$set\n;
}


Tres Bien!!! Merci Beaucoup!!

Thank you so much :)

I will pour over this code until I completely understand it. I knew I 
came to the right place!


Steve

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Re: Can recursion eliminate nested foreach() loops?

[Steve Bertrand]

On 2012-02-26 21:52, Shawn H Corey wrote:

On 12-02-26 09:30 PM, Steve Bertrand wrote:

I know this isn't a beginner's question, but I know there are geniuses
here. Is there a way to simplify this within Perl?


There is no simplify way of doing this. Separate off the first attribute
and cross-product it with a recursive call to the rest. Like this:


fyi: http://forums.devshed.com/perl-programming-6/recursion-help-882763.html

Steve

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Re: Can recursion eliminate nested foreach() loops?

[Rob Dixon]

On 27/02/2012 02:30, Steve Bertrand wrote:

I came across a question early this morning on a forum that intrigued
me. I literally spent about five hours trying everything to solve it,
but I couldn't.

Every attempt at recursion, counting, numbering, hashing etc failed. Is
there a way to use recursion to eliminate the repeated and
pre-calculated calls to foreach as this OP is asking?

 From ... .. ... is verbatim 'dms000'

...

I need to generate a list of combinations from a data structure such as:

my $attributes =
[
{ type = 'colors', values = [qw/red green blue/] },
{ type = 'sizes', values = [qw/small large/] },
{ type = 'shades', values = [qw/light dark/] },
];

It is easy enough when the number of types are known:

my @combos = ();
foreach my $a (@{$attributes-[0]-{values}}) {
foreach my $b (@{$attributes-[1]-{values}}) {
foreach my $c (@{$attributes-[2]-{values}}) {
push @combos, [$a, $b, $c];
}
}
}

Which results in a list such as:
red small light
red small dark
red large light
red large dark
green small light
...

But how to do with arbitrary number of types? Obviously will need
recursion but I can't figure it out. The only thing I could come up with
was generating code like code2 as a string and eval()ing it...a poor
solution.

...

I know this isn't a beginner's question, but I know there are geniuses
here. Is there a way to simplify this within Perl?


Hi Steve

Much of the complexity comes from working with the nested data
structure. Writing a subroutine that takes just a set of the 'values'
arrays cleans things up a lot. Take a look at the program below.

HTH,

Rob


use strict;
use warnings;

my $attributes = [
  { type = 'colors',  values = [qw/red green blue/]  },
  { type = 'sizes',   values = [qw/small large/] },
  { type = 'shades',  values = [qw/light dark/] },
];

print $_\n foreach combos(map $_-{values}, @$attributes);

sub combos {

  my $first = shift;

  return @$first unless @_;

  my @combinations;

  foreach my $beg (@$first) {
foreach my $end (combos(@_)) {
  push @combinations, $beg $end;
}
  }

  return @combinations;
}

**OUTPUT**

red small light
red small dark
red large light
red large dark
green small light
green small dark
green large light
green large dark
blue small light
blue small dark
blue large light
blue large dark

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Re: Can recursion eliminate nested foreach() loops?

[Steve Bertrand]

On 2012-02-26 23:55, Rob Dixon wrote:

On 27/02/2012 02:30, Steve Bertrand wrote:



I know this isn't a beginner's question, but I know there are geniuses
here. Is there a way to simplify this within Perl?


Hi Steve

Much of the complexity comes from working with the nested data
structure. Writing a subroutine that takes just a set of the 'values'
arrays cleans things up a lot. Take a look at the program below.


In my mind, I knew that map() had to fit in someplace, but by the time I 
thought about map, I was ready to ask for help instead of performing the 
Schwartzian Transform physically on my keyboard :)


This is another great piece of code I (and others) can study. I'm 
leaving it below. Thank you Rob!



use strict;
use warnings;

my $attributes = [
{ type = 'colors', values = [qw/red green blue/] },
{ type = 'sizes', values = [qw/small large/] },
{ type = 'shades', values = [qw/light dark/] },
];

print $_\n foreach combos(map $_-{values}, @$attributes);

sub combos {

my $first = shift;

return @$first unless @_;

my @combinations;

foreach my $beg (@$first) {
foreach my $end (combos(@_)) {
push @combinations, $beg $end;
}
}

return @combinations;
}


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Re: Foreach loop and hash of arrays

[Rob Dixon]

On 07/02/2012 01:39, sono...@fannullone.us wrote:

On Feb 6, 2012, at 1:42 PM, Steve Bertrand wrote:


This may be easier. It uses the hash elements directly as an
array, then uses grep to see if the zip code is within the specific
state. It returns true if the state owns that zip code, and false
if it doesn't.

if ( grep( /^$customers_zip$/, @{ $states{ $customers_state } } ) ) {
$match = yes;
}


Thanks, Steve.  Elegantly simple!


It is odd to use a regex here when the intention is a simple string
comparison

  grep( $_ eq $customers_zip, @{ $states{ $customers_state } } )

in fact, if the objective is to reduce the code to something as brief as
possible then this will do the trick

  my $match = (grep $_ eq $customers_zip, @{$states{$customers_state}}) 
? 'yes' : 'no';


Rob

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Re: Foreach loop and hash of arrays

[Shawn H Corey]

On 12-02-07 06:26 AM, Rob Dixon wrote:

in fact, if the objective is to reduce the code to something as brief as
possible then this will do the trick

   my $match = (grep $_ eq $customers_zip, @{$states{$customers_state}})
? 'yes' : 'no';


You can use first from List::Util for more efficient code:

  use List::Util qw( first );
  my $match = (first { $_ eq $customers_zip } 
@{$states{$customers_state}}) ? 'yes' : 'no';



--
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  Shawn

Programming is as much about organization and communication
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Foreach loop and hash of arrays

[sono-io]

I have a web form where people enter their address info and I want to 
make sure that the first three digits of their Zip Code correspond to their 
State.

So I'm creating a hash of arrays that contains a list of Zip Codes for 
the United States.  I've also written a foreach loop to access this hash but 
I'd like to see if it could be written better.  For example, do I really need 
three foreach loops?

Also, the first line that's printed contains 499 and I can't figure 
out where that's coming from.

I'd appreciate some help.

Thanks,
Marc



#!/Users/perl5/perlbrew/perls/perl-5.14.1/bin/perl
use strict;
use warnings;

my %states = (
AL = [ '350','351', ],
AK = [ '995','996', ],
AZ = [ '850','851', ],
AR = [ '716','717', ],
);

my $customers_state = 'AZ';
my $customers_zip = '850';
my $match = 'no' ;

STATE:  foreach my $state (keys %states) {
#   print $state \n;
if ($state eq $customers_state) {
foreach (@{$states{$customers_state}}) {
my @zips = $_;
ZIP:foreach my $zip (@zips) {
next ZIP if $zip ne 
$customers_zip;
$match = 'yes';
#   print \nZip matches 
the State \n;
}
}
last STATE;
}
}
print $match;



SAMPLE OUTPUT:

499
yes


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Re: Foreach loop and hash of arrays

[Steve Bertrand]

On 2012.02.06 16:14, sono...@fannullone.us wrote:

I have a web form where people enter their address info and I want to 
make sure that the first three digits of their Zip Code correspond to their 
State.

So I'm creating a hash of arrays that contains a list of Zip Codes for 
the United States.  I've also written a foreach loop to access this hash but 
I'd like to see if it could be written better.  For example, do I really need 
three foreach loops?

Also, the first line that's printed contains 499 and I can't figure 
out where that's coming from.

I'd appreciate some help.

Thanks,
Marc



#!/Users/perl5/perlbrew/perls/perl-5.14.1/bin/perl
use strict;
use warnings;

my %states = (
AL =  [ '350','351', ],
AK =  [ '995','996', ],
AZ =  [ '850','851', ],
AR =  [ '716','717', ],
);

my $customers_state = 'AZ';
my $customers_zip = '850';
my $match = 'no' ;

STATE:  foreach my $state (keys %states) {
#   print $state \n;
if ($state eq $customers_state) {
foreach (@{$states{$customers_state}}) {
my @zips = $_;
ZIP:foreach my $zip (@zips) {
next ZIP if $zip ne 
$customers_zip;
$match = 'yes';
#   print \nZip matches the 
State \n;
}
}
last STATE;
}
}
print $match;



SAMPLE OUTPUT:

499
yes


This may be easier. It uses the hash elements directly as an array, then 
uses grep to see if the zip code is within the specific state. It 
returns true if the state owns that zip code, and false if it doesn't. 
Therefore, if it is true, $match will be set to yes.


#!/usr/bin/perl
use strict;
use warnings;

my %states = (
AL = [ '350','351', ],
AK = [ '995','996', ],
AZ = [ '850','851', ],
AR = [ '716','717', ],
);

my $customers_state = 'AR';
my $customers_zip = '716';
my $match = 'no' ;

if ( grep( /^$customers_zip$/, @{ $states{ $customers_state } } ) ) {
$match = yes;
}

print $match\n;

Steve

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Re: Foreach loop and hash of arrays

[Parag Kalra]

On Mon, Feb 6, 2012 at 1:14 PM, sono...@fannullone.us wrote:

For example, do I really need three foreach loops?




You can get rid of third ForLoop for sure.

use strict;
use warnings;

my %states = (
   AL = [ '350','351', ],
   AK = [ '995','996', ],
   AZ = [ '850','851', ],
   AR = [ '716','717', ],
);

my $customers_state = 'AZ';
my $customers_zip = '850';
my $match = 'no' ;

STATE: foreach my $state (keys %states) {
   if ($state eq $customers_state) {
   foreach (@{$states{$customers_state}}) {
   my @zips = $_;
   $match = 'yes' if grep /$customers_zip/, @zips ;
   last STATE;
   }
   }
}
print $match;

Re: Foreach loop and hash of arrays

[Rob Dixon]

On 06/02/2012 21:14, sono...@fannullone.us wrote:

use strict;
use warnings;

my %states = (
AL =  [ '350','351', ],
AK =  [ '995','996', ],
AZ =  [ '850','851', ],
AR =  [ '716','717', ],
);

my $customers_state = 'AZ';
my $customers_zip = '850';
my $match = 'no' ;

STATE:  foreach my $state (keys %states) {
#   print $state \n;
if ($state eq $customers_state) {
foreach (@{$states{$customers_state}}) {
my @zips = $_;
ZIP:foreach my $zip (@zips) {
next ZIP if $zip ne 
$customers_zip;
$match = 'yes';
#   print \nZip matches the 
State \n;
}
}
last STATE;
}
}
print $match;




You are missing the point of hashes: that they can be indexed directly 
by a key value, and there is no need to loop through all elements of the 
has. You can reduce you code to just one loop:


  foreach my $zip (@{$states{$customers_state}}) {
if ($zip eq $customers_zip) {
  $match = 'yes';
  last;
}
  }


HTH,

Rob

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Re: Foreach loop and hash of arrays

[Uri Guttman]

On 02/06/2012 04:58 PM, Parag Kalra wrote:

On Mon, Feb 6, 2012 at 1:14 PM,sono...@fannullone.us  wrote:


For example, do I really need three foreach loops?





You can get rid of third ForLoop for sure.


you don't actually lose the third loop. grep is an implied loop.




STATE: foreach my $state (keys %states) {
if ($state eq $customers_state) {
foreach (@{$states{$customers_state}}) {


use a named variable there.


my @zips = $_;


that assigns an array ref to @zips and not the list of zips. you need to 
dereference it. and you don't need a temp var as you can do that in the 
grep itself.



$match = 'yes' if grep /$customers_zip/, @zips ;
last STATE;


why the last call there? it means the double loop only executes one time.

uri


}
}
}
print $match;




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Re: Foreach loop and hash of arrays

[Robert Wohlfarth]

On Mon, Feb 6, 2012 at 3:14 PM, sono...@fannullone.us wrote:

So I'm creating a hash of arrays that contains a list of Zip Codes
 for the United States.  I've also written a foreach loop to access this
 hash but I'd like to see if it could be written better.  For example, do I
 really need three foreach loops?

snip

 #!/Users/perl5/perlbrew/perls/perl-5.14.1/bin/perl
 use strict;
 use warnings;

 my %states = (
AL = [ '350','351', ],
AK = [ '995','996', ],
AZ = [ '850','851', ],
AR = [ '716','717', ],
 );

 my $customers_state = 'AZ';
 my $customers_zip = '850';
 my $match = 'no' ;

 STATE:  foreach my $state (keys %states) {
 #   print $state \n;
if ($state eq $customers_state) {
foreach (@{$states{$customers_state}}) {
my @zips = $_;
 ZIP:foreach my $zip (@zips) {
next ZIP if $zip ne
 $customers_zip;
$match = 'yes';
 #   print \nZip
 matches the State \n;
}
}
last STATE;
}
}
 print $match;


You can also key the hash with the first three digits and skip the loops
altogether.


 my %zips = (
350 = 'AL',
351 = 'AL',
995 = 'AK',
996 = 'AK',
850 = 'AZ',
851 = 'AZ',
716 = 'AR',
717 = 'AR',
);

 my $customers_state = 'AZ';
my $customers_zip = '850';

if (
exists( $zips{$customers_zip} )
and $zips{$customers_zip} eq $customers_state
) { print 'yes'; }
else { print 'no'; }

-- 
Robert Wohlfarth

Re: Foreach loop and hash of arrays

[sono-io]

On Feb 6, 2012, at 1:42 PM, Steve Bertrand wrote:

 This may be easier. It uses the hash elements directly as an array, then uses 
 grep to see if the zip code is within the specific state. It returns true if 
 the state owns that zip code, and false if it doesn't.
 
 if ( grep( /^$customers_zip$/, @{ $states{ $customers_state } } ) ) {
$match = yes;
 }

Thanks, Steve.  Elegantly simple!

Marc
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Re: Question/Problem with foreach loop

[CM Analyst]

Gents, 

Sorry for my delayed response. Thank you for your suggestions. Based on your 
feedback, I made the following changes, and the hook is now working as expected.

Thanks a million!

my $taskstate = $taskEntity-GetFieldValue(state)-GetValue();

    $session-OutputDebugString (Task's state is $taskstate\n);
     
  next if $taskstate eq Completed;
      


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Using $variable outside a foreach loop

[sono-io]

Maybe it's too early in the morning here, but I can't seem to remember 
how to use a lexical $variable that is defined inside a foreach loop, outside 
of that loop.=:\

Here's the loop:

foreach my $name (split (/, */, $names)) {
next unless ($name =~ /\w/);
my $sortstr = substr(00$totalcells, -2);
$html =~ s|/tdtd|/td\ntd|g;
$cell{$sortstr$name} = !--//CELL $name//--;
$cell{$sortstr$name} =~ s/\[NAME\]/$name/sig;
$totalcells++;
}

I want to use $name in another loop just after this one, but when I 
do, I get Global symbol $name requires explicit package.

Could someone please point me in the right direction?

Thanks,
Marc
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Re: Using $variable outside a foreach loop

[Alan Haggai Alavi]

Hello,

   foreach my $name (split (/, */, $names)) {

Here, the scope of $name is limited to the foreach loop and not outside it. 
So, you will have to declare the variable again for use outside the loop.

Regards,
Alan Haggai Alavi.
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Re: Using $variable outside a foreach loop

[sono-io]

On Jun 3, 2011, at 8:45 AM, Alan Haggai Alavi wrote:

 Here, the scope of $name is limited to the foreach loop and not outside it. 
 So, you will have to declare the variable again for use outside the loop.

But wouldn't that make the second $name a different variable?  I'm 
not at my computer to try it.

Marc
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Re: Using $variable outside a foreach loop

[Jim Gibson]

At 8:37 AM -0700 6/3/11, sono...@fannullone.us wrote:
	Maybe it's too early in the morning here, but I can't seem to 
remember how to use a lexical $variable that is defined inside a 
foreach loop, outside of that loop.=:\


Here's the loop:

foreach my $name (split (/, */, $names)) {
next unless ($name =~ /\w/);
my $sortstr = substr(00$totalcells, -2);
$html =~ s|/tdtd|/td\ntd|g;
$cell{$sortstr$name} = !--//CELL $name//--;
$cell{$sortstr$name} =~ s/\[NAME\]/$name/sig;
$totalcells++;
}

	I want to use $name in another loop just after this one, 
but when I do, I get Global symbol $name requires explicit package.


Declare the variable just before the loop, and remove the 'my' from 
the foreach statement:


my $name;
foreach $name ( ... ) {
  ...
}


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j...@gibson.org

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Re: Using $variable outside a foreach loop

[C.DeRykus]

On Jun 3, 8:37 am, sono...@fannullone.us wrote:
 ...
         I want to use $name in another loop just after this one, but when I 
 do, I get Global symbol $name requires explicit package.


One option is an outer enclosing block that'll
extend the scope of $name to that entire block:

{   # enclosing block
   my $name;
   for $name ( split //... ) { }   #  first loop
   for $name ( ... )  { }   #  next loop
}

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Charles DeRykus


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Re: Using $variable outside a foreach loop

[sono-io]

C.DeRykus wrote:

 One option is an outer enclosing block that'll extend the scope of $name to 
 that entire block:

Jim Gibson wrote:

 Declare the variable just before the loop, and remove the 'my' from the 
 foreach statement:


Thanks for the responses.  I was able to get it to work.

Marc
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Re: Using $variable outside a foreach loop

[Shawn H Corey]

On 11-06-03 11:37 AM, sono...@fannullone.us wrote:

I want to use $name in another loop just after this one, but when I do, I get 
Global symbol $name requires explicit package.

Could someone please point me in the right direction?


Certainly.  The variable used in a foreach loop is independent of 
anything outside the loop.  Even if it's declared before the loop, it's 
value is unavailable inside the loop:


#!/usr/bin/env perl

use strict;
use warnings;

my $name = 'forgotten';

for $name ( qw( fred barney wilma )){
  print \$name is $name\n;
}

print \$name is $name\n;
__END__

Outside the loop, it becomes just another variable.


--
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  Shawn

Confusion is the first step of understanding.

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as it is about coding.

The secret to great software:  Fail early  often.

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Re: Using $variable outside a foreach loop

[Uri Guttman]

 s == sono-io  sono...@fannullone.us writes:

  sMaybe it's too early in the morning here, but I can't seem to remember 
how to use a lexical $variable that is defined inside a foreach loop, outside 
of that loop.=:\
  sHere's the loop:

  sforeach my $name (split (/, */, $names)) {
  snext unless ($name =~ /\w/);
  smy $sortstr = substr(00$totalcells, -2);

that looks like you are forcing leading 0's. the common idiom for that
is sprintf %02d, $totalcells. your way works but is harder to read.

  s$html =~ s|/tdtd|/td\ntd|g;

why are you doing that insert of a newline each time in that loop? you
don't use or modify $html anywhere else in this loop. 

  s$cell{$sortstr$name} = !--//CELL $name//--;
  s$cell{$sortstr$name} =~ s/\[NAME\]/$name/sig;

you just assigned that value the line before. unless $name has [NAME]
inside it, how could that s/// op ever do anything?

  s$totalcells++;
  s}

  sI want to use $name in another loop just after this one, but when I 
do, I get Global symbol $name requires explicit package.

did you want to use $name as the loop variable again? that is perfectly
fine as this $name is scoped only to that loop. if you just want to use
$name for any other reason you need to just declare it with my.

uri

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Re: Using $variable outside a foreach loop

[Brian Fraser]

On Fri, Jun 3, 2011 at 1:23 PM, Jim Gibson jimsgib...@gmail.com wrote:

 Declare the variable just before the loop, and remove the 'my' from the
 foreach statement:

 my $name;
 foreach $name ( ... ) {
  ...
 }


That won't do. What that code actually translated to is
my $name;
for my $name ( ... ) { ... }

With the second $name masking the first! IIRC this is explained somewhere in
PBP, but I don't have the book at hand right now. In any case, if you want
to use the variable outside of the for, don't name the two variables the
same.
The rough rule of thumb is that leaving off the my in a for(each) is
probably introducing subtle bugs into your program.

Brian.

Re: Using $variable outside a foreach loop

[Uri Guttman]

 BF == Brian Fraser frase...@gmail.com writes:

  BF On Fri, Jun 3, 2011 at 1:23 PM, Jim Gibson jimsgib...@gmail.com wrote:
   Declare the variable just before the loop, and remove the 'my' from the
   foreach statement:
   
   my $name;
   foreach $name ( ... ) {
   ...
   }
   

  BF That won't do. What that code actually translated to is
  BF my $name;
  BF for my $name ( ... ) { ... }

not true. 

perl -le 'my $x = zzz ; for $x ( qw( foo bar ) ) { print L: $x } print E: 
$x'
L: foo
L: bar
E: zzz

foreach without a my will localize the loop variable. that isn't the
same as my.

  BF With the second $name masking the first! IIRC this is explained
  BF somewhere in PBP, but I don't have the book at hand right now. In
  BF any case, if you want to use the variable outside of the for,
  BF don't name the two variables the same.  The rough rule of thumb is
  BF that leaving off the my in a for(each) is probably introducing
  BF subtle bugs into your program.

why search PBP when the perldocs are very clear about it and easily
searched?

from perldoc perlsyn:

The foreach loop iterates over a normal list value and sets
the variable VAR to be each element of the list in turn.  If the
variable is preceded with the keyword my, then it is lexically
scoped, and is therefore visible only within the loop.
Otherwise, the variable is implicitly local to the loop and
regains its former value upon exiting the loop.  If the variable
was previously declared with my, it uses that variable instead
of the global one, but it's still localized to the loop.  This
implicit localisation occurs only in a foreach loop.

so in my oneliner the my allowed the $x to not need redeclaring in the
foreach but it still localized the value to the loop.

but as i said in another post, the OP just likely wants to use $name as
a loop var again which he can with another my declare.

uri

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Re: Using $variable outside a foreach loop

[sono-io]

On Jun 3, 2011, at 10:22 AM, Uri Guttman wrote:

 smy $sortstr = substr(00$totalcells, -2);
 that looks like you are forcing leading 0's. the common idiom for that
 is sprintf %02d, $totalcells. your way works but is harder to read.

Thanks, Uri.  I didn't catch that.

I didn't write this script.  I'm using it to learn from and cleaning it 
up at the same time.  I know that learning Perl from an older script probably 
isn't the best way to do it, but since I have a vested interest in how this 
script works, it's forcing me to learn it faster than I would otherwise.  
However, if anyone knows of a shopping cart written in modern perl, I'd love to 
have a look.

 s$html =~ s|/tdtd|/td\ntd|g;
 why are you doing that insert of a newline each time in that loop? you
 don't use or modify $html anywhere else in this loop. 

Actually, it's being used on an HTML template and just makes the HTML 
code look cleaner.

 s   I want to use $name in another loop just after this one, but when I 
 do, I get Global symbol $name requires explicit package.
 did you want to use $name as the loop variable again? that is perfectly
 fine as this $name is scoped only to that loop. if you just want to use
 $name for any other reason you need to just declare it with my.

I wasn't very clear in what I wanted.  Sorry.  I wanted to use the 
value of $name in another loop but after testing, it looks like Shawn was 
correct when he wrote:

 The variable used in a foreach loop is independent of anything outside the 
 loop.

I actually had to use another variable in the second loop to grab the 
name.

Thanks to everyone who responded.  I got it to work now.

Marc
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Re: Using $variable outside a foreach loop

[Shawn H Corey]

On 11-06-03 03:58 PM, sono...@fannullone.us wrote:

I wasn't very clear in what I wanted.  Sorry.  I wanted to use the value of 
$name in another loop but after testing


That implies something is wrong with your logic.  The question is:  what 
value of $name do you want?  The first?  The last?  Either you want the 
second loop nested in the first, or you want a completely independent 
one that iterates through all the values.



--
Just my 0.0002 million dollars worth,
  Shawn

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as it is about coding.

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Re: Using $variable outside a foreach loop

[sono-io]

On Jun 3, 2011, at 1:38 PM, Shawn H Corey wrote:

 That implies something is wrong with your logic.

Yep.  I came to the same conclusion. =:)

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Re: Using $variable outside a foreach loop

[Dr.Ruud]

On 2011-06-03 17:37, sono...@fannullone.us wrote:


Maybe it's too early in the morning here, but I can't seem to remember 
how to use a lexical $variable that is defined inside a foreach loop, outside 
of that loop.=:\

Here's the loop:

foreach my $name (split (/, */, $names)) {
next unless ($name =~ /\w/);
my $sortstr = substr(00$totalcells, -2);
$html =~ s|/tdtd|/td\ntd|g;
$cell{$sortstr$name} = !--//CELL $name//--;
$cell{$sortstr$name} =~ s/\[NAME\]/$name/sig;
$totalcells++;
}

I want to use $name in another loop just after this one, but when I do, I get 
Global symbol $name requires explicit package.

Could someone please point me in the right direction?


What would be the use of that?

If you declare $name before the loop, it will (after leaving the loop) 
have the last value assigned to it. What would you want that for?


To me, yours is an X-Y problem. (see google)

You should probably just declare a new variable for the other loop.

--
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Re: Using $variable outside a foreach loop

[Uri Guttman]

 R == Ruud  rvtol+use...@isolution.nl writes:

  R On 2011-06-03 17:37, sono...@fannullone.us wrote:
   Maybe it's too early in the morning here, but I can't seem to remember how 
to use a lexical $variable that is defined inside a foreach loop, outside of 
that loop.=:\
   
   Here's the loop:
   
   foreach my $name (split (/, */, $names)) {
   next unless ($name =~ /\w/);
   my $sortstr = substr(00$totalcells, -2);
   $html =~ s|/tdtd|/td\ntd|g;
   $cell{$sortstr$name} = !--//CELL $name//--;
   $cell{$sortstr$name} =~ s/\[NAME\]/$name/sig;
   $totalcells++;
   }
   
   I want to use $name in another loop just after this one, but when I do, 
I get Global symbol $name requires explicit package.
   
   Could someone please point me in the right direction?

  R What would be the use of that?

  R If you declare $name before the loop, it will (after leaving the loop)
  R have the last value assigned to it. What would you want that for?

not true. see a post i made with a one liner. $name is localized (if not
my) so the previous value before the loop is seen after the loop. loop
values don't affect the outer $name at all.

uri

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Re: Using $variable outside a foreach loop

[shawn wilson]

On Jun 3, 2011 3:17 PM, Uri Guttman u...@stemsystems.com wrote:



 perl -le 'my $x = zzz ; for $x ( qw( foo bar ) ) { print L: $x } print
E: $x'
 L: foo
 L: bar
 E: zzz


That's odd, I would have thought that would have given 'foo bar bar'. So,
how would you keep data from a loop once you're outside of the loop?

Re: Using $variable outside a foreach loop

[Uri Guttman]

 sw == shawn wilson ag4ve...@gmail.com writes:

  sw On Jun 3, 2011 3:17 PM, Uri Guttman u...@stemsystems.com wrote:
   

   
   perl -le 'my $x = zzz ; for $x ( qw( foo bar ) ) { print L: $x } print
  sw E: $x'
   L: foo
   L: bar
   E: zzz

  sw That's odd, I would have thought that would have given 'foo bar bar'. So,
  sw how would you keep data from a loop once you're outside of the loop?

you don't use a loop variable for that. just declare it before the loop,
assign as needed inside the loop and it will be there. if that gets
messy as it can, i change the code to use a sub with the loop inside and
return the value. 

uri

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Re: script takes long time to run when comparing digits within strings using foreach

[Dr.Ruud]

On 2011-05-27 10:18, eventual wrote:


I have an array , @datas, and each element within @datas is a string that's 
made up of 6 digits with spaces in between like this “1 2 3 4 5 6”, so the 
array look like this
@datas = ('1 2 3 4 5 6', '1 2 9 10 11 12', '1 2 3 4 5 8', '1 2 3 4 5 9' , '6 7 
8 9 10 11');
Now I wish to compare each element of @datas with the rest of the elements in 
@datas in such a way that if 5 of the digits match, to take note of the 
matching indices,  and so the script I wrote is appended below.


a. Do once what you can do only once. There are at least 2 points where 
you didn't: 1. prepare @datas before looping; 2. don't compare the same 
stuff more than once.


b. Assemble a result, and report at the end. Don't use any 'shared 
resources' like incrementing global counters while going along.



#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

my @data = DATA;
$_ = { map { $_ = 1 } split } for @data;
$ARGV[0] and print Dumper( \@data );

my @result;

for my $i ( 0 .. $#data - 1 ) {
my @k = keys %{ $data[ $i ] };
for my $j ( $i + 1 .. $#data ) {
my $n = 0;
exists $data[ $j ]{ $_ } and ++$n for @k;
$n = 5 and push @result, [ $i, $j ];
}
}

print Dumper( \@result );

__DATA__
1 2 3 4 5 6
1 2 9 10 11 12
1 2 3 4 5 8
1 2 3 4 5 9
6 7 8 9 10 11


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Re: script takes long time to run when comparing digits within strings using foreach

[John W. Krahn]

eventual wrote:

Hi,


Hello,


I have an array , @datas, and each element within @datas is a string
that's made up of 6 digits with spaces in between like this “1 2 3 4 5
6”, so the array look like this
@datas = ('1 2 3 4 5 6', '1 2 9 10 11 12', '1 2 3 4 5 8', '1 2 3 4 5
9' , '6 7 8 9 10 11');
Now I wish to compare each element of @datas with the rest of the
elements in @datas in such a way that if 5 of the digits match, to
take note of the matching indices,  and so the script I wrote is
appended below.
However, the script below takes a long time to run if the datas at
@datas are huge( eg 30,000 elements). I then wonder is there a way to
rewrite the script so that the script can run faster.
Thanks

## script below ###

#!/usr/bin/perl
use strict;

my @matched_location = ();
my @datas = ('1 2 3 4 5 6', '1 2 9 10 11 12', '1 2 3 4 5 8', '1 2 3 4 5 9' , '6 
7 8 9 10 11');

my $iteration_counter = -1;
foreach (@datas){
$iteration_counter++;
my $reference = $_;

my $second_iteration_counter = -1;
my $string = '';
foreach (@datas){
   $second_iteration_counter++;
   my @individual_digits = split / /,$_;

   my $ctr = 0;
   foreach(@individual_digits){
   if($reference =~/^$_ | $_ | $_$/){
   $ctr++;
   }
   }
   if ($ctr= 5){
   $string = $string . $second_iteration_counter ;
   }
}
$matched_location[$iteration_counter] = $string;
}

my $ctr = -1;
foreach(@matched_location){
 $ctr++;
 print Index $ctr of \@matched_location = $_\n;
}



Your program can be reduced to:

my @matched_location;
my @datas = ( '1 2 3 4 5 6', '1 2 9 10 11 12', '1 2 3 4 5 8', '1 2 3 4 5 
9', '6 7 8 9 10 11' );



for my $i ( 0 .. $#datas ) {
for my $j ( 0 .. $#datas ) {
$matched_location[ $i ] .= $j  if 5 = grep $datas[ $i ] =~ 
/(?:^|(?= ))$_(?= |$)/, split ' ', $datas[ $j ]

}
}

print map Index $_ of \@matched_location = $matched_location[$_]\n, 0 
.. $#matched_location;


You should benchmark it to see if it is any faster than your original code.



John
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more complex... It takes a touch of genius -
and a lot of courage to move in the opposite
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script takes long time to run when comparing digits within strings using foreach

[eventual]

Hi,
I have an array , @datas, and each element within @datas is a string that's 
made up of 6 digits with spaces in between like this “1 2 3 4 5 6”, so the 
array look like this 
@datas = ('1 2 3 4 5 6', '1 2 9 10 11 12', '1 2 3 4 5 8', '1 2 3 4 5 9' , '6 7 
8 9 10 11');
Now I wish to compare each element of @datas with the rest of the elements in 
@datas in such a way that if 5 of the digits match, to take note of the 
matching indices,  and so the script I wrote is appended below.
However, the script below takes a long time to run if the datas at @datas are 
huge( eg 30,000 elements). I then wonder is there a way to rewrite the script 
so that the script can run faster.
Thanks
 
## script below ###
 
#!/usr/bin/perl
use strict;
 
my @matched_location = ();
my @datas = ('1 2 3 4 5 6', '1 2 9 10 11 12', '1 2 3 4 5 8', '1 2 3 4 5 9' , '6 
7 8 9 10 11');
 
my $iteration_counter = -1;
foreach (@datas){
   $iteration_counter++;
   my $reference = $_;
 
   my $second_iteration_counter = -1;
   my $string = '';
   foreach (@datas){
  $second_iteration_counter++;
  my @individual_digits = split / /,$_;
 
  my $ctr = 0;
  foreach(@individual_digits){
  if($reference =~/^$_ | $_ | $_$/){
  $ctr++;
  }
  }
  if ($ctr = 5){
  $string = $string . $second_iteration_counter ;
  }
   }
   $matched_location[$iteration_counter] = $string;
}
 
my $ctr = -1;
foreach(@matched_location){
    $ctr++;
    print Index $ctr of \@matched_location = $_\n;
}
 

Re: script takes long time to run when comparing digits within strings using foreach

[Shlomi Fish]

Hi eventual,

On Friday 27 May 2011 11:18:01 eventual wrote:
 Hi,
 I have an array , @datas, and each element within @datas is a string that's
 made up of 6 digits with spaces in between like this “1 2 3 4 5 6”, so the
 array look like this @datas = ('1 2 3 4 5 6', '1 2 9 10 11 12', '1 2 3 4 5
 8', '1 2 3 4 5 9' , '6 7 8 9 10 11'); Now I wish to compare each element
 of @datas with the rest of the elements in @datas in such a way that if 5
 of the digits match, to take note of the matching indices,  and so the
 script I wrote is appended below. However, the script below takes a long
 time to run if the datas at @datas are huge( eg 30,000 elements). I then
 wonder is there a way to rewrite the script so that the script can run
 faster. Thanks
  
 ## script below ###
  
 #!/usr/bin/perl
 use strict;
  
 my @matched_location = ();
 my @datas = ('1 2 3 4 5 6', '1 2 9 10 11 12', '1 2 3 4 5 8', '1 2 3 4 5 9'
 , '6 7 8 9 10 11'); 
 my $iteration_counter = -1;
 foreach (@datas){
$iteration_counter++;
my $reference = $_;
  
my $second_iteration_counter = -1;
my $string = '';
foreach (@datas){
   $second_iteration_counter++;
   my @individual_digits = split / /,$_;
  
   my $ctr = 0;
   foreach(@individual_digits){
   if($reference =~/^$_ | $_ | $_$/){
   $ctr++;
   }
   }
   if ($ctr = 5){
   $string = $string . $second_iteration_counter ;
   }
}
$matched_location[$iteration_counter] = $string;
 }
  
 my $ctr = -1;
 foreach(@matched_location){
 $ctr++;
 print Index $ctr of \@matched_location = $_\n;
 }
  

First of all, you should add use warnings; to your code. Then you should get 
rid of the implicit $_ as loop iterator because it's easy to break. For more 
information see:

http://perl-begin.org/tutorials/bad-elements/

Other than that - you should use a better algorithm. One option would be to 
sort the integers and then use a diff/merge-like algorithm:

http://en.wikipedia.org/wiki/Merge_algorithm

A different way would be to use a hash to count the number of times each 
number occured in the two sets, and then see how many of them got a value of 2 
(indicating they are in both sets).

But at the moment, everything is very inefficient there.

Regards,

Shlomi Fish


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Star Trek: We, the Living Dead - http://shlom.in/st-wtld

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then I remember - because they are so pedantic.
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Question/Problem with foreach loop

[CM Analyst]

Hi,

In this code, the intent is to iterate through the tasks and modify the ID 
field. The Task record (entity) should not be modified if it's state equals 
Completed. 

When I run this routine, there are two problems:

Problem 1) The if statement is not being evaluated. The record (even if it's 
in the Completed state is being modified.

Problem 2) Subsequent records (ie any record after the first one is not 
modfied). In other words, if I have multiple records, just the first one in the 
list gets modified. All others are skipped.

Can someone help me figure out where I am going wrong with this? Thanks.

snip

# Iterate through all tasks

foreach (@$tasks) {

# Get a task entity for the current taskid (in $_)

my $taskEntity = $session-GetEntity ('almtask', $_);

$taskEntity-GetFieldValue(state)-GetValue();

if ($taskEntity eq Completed) {return;}

# did not work# if ($taskEntity eq Completed) {return '';}
# did not work# if ($taskEntity eq Completed) {exit 1;}
 
else {

$session-OutputDebugString (Setting task entity to modify\n);

# Modify this task...
$taskEntity-EditEntity ('Modify');

$session-OutputDebugString (Modifying task\n);

$session-OutputDebugString (Setting task's project id to $ProjectID);

# Set the project field to the new ProjectID
my $returnMsg = $taskEntity-SetFieldValue ('project', $ProjectID);

return $returnMsg unless $returnMsg eq '';

snip

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Re: Question/Problem with foreach loop

[Jim Gibson]

On 5/18/11 Wed  May 18, 2011  5:06 PM, CM Analyst cmanal...@yahoo.com
scribbled:

 Hi,
 
 In this code, the intent is to iterate through the tasks and modify the ID
 field. The Task record (entity) should not be modified if it's state equals
 Completed. 
 
 When I run this routine, there are two problems:
 
 Problem 1) The if statement is not being evaluated. The record (even if it's
 in the Completed state is being modified.
 
 Problem 2) Subsequent records (ie any record after the first one is not
 modfied). In other words, if I have multiple records, just the first one in
 the list gets modified. All others are skipped.
 
 Can someone help me figure out where I am going wrong with this? Thanks.
 
 snip
 
 # Iterate through all tasks
 
 foreach (@$tasks) {

You would be better to use an explicit variable here rather than the default
$_, especially since you are calling methods in the loop that might modify
the value of $_:

  foreach my $task ( @$tasks ) {

 
 # Get a task entity for the current taskid (in $_)
 
 my $taskEntity = $session-GetEntity ('almtask', $_);

We don't know what $session contains and what GetEntity does.

 
 $taskEntity-GetFieldValue(state)-GetValue();

You have a bareword here (state). If this is supposed to be a string, then
you should quote it. state could be a function (or even a keyword in later
Perls):

  $taskEntity-GetFieldValue('state')-GetValue();

Do you have 'use strict;' in your program.

 
 if ($taskEntity eq Completed) {return;}

You probably don't want 'return' here. If you want to skip this task and go
to the next one in the loop, then you should use 'next'. 'return' will exit
from a function (although we don't know if this code is in a function since
you haven't shown us the whole code.):

  next if $taskEntity eq 'Completed';




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Re: Question/Problem with foreach loop

[Uri Guttman]

 CA == CM Analyst cmanal...@yahoo.com writes:

  CA my $taskEntity = $session-GetEntity ('almtask', $_);

that gets a perl object in $taskEntity.

  CA $taskEntity-GetFieldValue(state)-GetValue();

where is the value being assigned to? $taskEntity is not being modified
or set in that line of code. it is just the object used to make the
call.

  CA if ($taskEntity eq Completed) {return;}

since that is the object, it will never eq Completed. you need to save
the value from the previous line and compare that. this should work:

my $value = $taskEntity-GetFieldValue(state)-GetValue();

if ( $value eq Completed) {
return;
}

see how that saves the value in a variable and then compares to that
variable. you need to learn more about OO in perl and how to
differentiate an object from the values that methods can return.

uri

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Re: foreach loop

[Chris Stinemetz]

Thanks Rob. That seems to have done the trick. I understand this is a
for loop, but do you mind breaking it down line by line so I fully
understand what it is doing?

Thank you,

Chris

  for my $i (44..47) {
    my $rlp = $data[$i];
    $sum{$cell}{$sect}{$carr}{$dist} += $rlp if $rlp;
  }


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Re: foreach loop

[Jim Gibson]

On 3/25/11 Fri  Mar 25, 2011  9:11 AM, Chris Stinemetz
chrisstinem...@gmail.com scribbled:

 Thanks Rob. That seems to have done the trick. I understand this is a
 for loop, but do you mind breaking it down line by line so I fully
 understand what it is doing?

My name isn't Rob, but I can give you a line-by-line description.

 
  for my $i (44..47) {

$i is a lexically-scoped scalar variable that will have the values 44, 45,
46, and 47 through four successive iterations of the statements enclosed by
the for loop.

    my $rlp = $data[$i];

$rlp is a lexically-scoped variable that will be assigned a value fetched
from the 44th, 45th, etc. element of the @data array.

    $sum{$cell}{$sect}{$carr}{$dist} += $rlp if $rlp;

The value assigned to $rlp in the previous line will be added to the value
in the element of a four-level nested hash as indexed by the values of
$cell, $sect, $carr, and $dist if and only if the value of $rlp evaluates to
true. This will be true for all values other than '', 0, and undef, so no
addition of undefined values will occur. Numerical conversions of the hash
element and the scalar variable are possible, depending upon what their
values are.

  }

End of for loop.



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RE: foreach loop

[Chris Stinemetz]

Thanks again Jim!

I have one more question..lol

I appreciate all your help!

I would like $dist be part of the print statement, but I am not sure how to 
code it correctly.

I am getting the following error:


Global symbol @dist requires explicit package name at ./jim.pl line 38.
Execution of ./banding aborted due to compilation errors.



#!/usr/bin/perl

use warnings;
use strict;

#my $filepath = 'C:/temp/PCMD';
# my $filepath = '/home/cstinemetz/perl_programs/1.EVDOPCMD';
# my $outfile  = 'output.txt';

# open my $fh, '', $filepath or die ERROR opening $filepath: $!;
# open my $out, '', $outfile or die ERROR opening $outfile: $!;

my %sum;

while (DATA){
next unless /;/;
chomp;
my @data = split /;/;
my($cell,$sect,$chan,$carr,$rlp1,$rlp2,$rlp3,$rlp4,$dist,$precis) =
  @data[31,32,38,39,44,45,46,47,261,262];

$carr = 
( $cell  299  $chan == 175 )  ? 2 : 
( $chan == 1025 )  ? 2 : 1 ; #nested ternary 
operator 

$dist = 
( length( $dist )  1 ) ? $dist/6.6/8/2*10/10 : 0 ;
  
  
$sum{$cell}{$sect}{$carr} += $rlp1 += $rlp2 += $rlp3 += $rlp4 || 0 ; }



my @data;
for my $cell ( sort keys %sum ) {
for my $sect ( sort keys %{$sum{$cell}} ) {
for my $carr ( sort keys %{$sum{$cell}{$sect}} 
) {
push( @data, [$dist[ $sum{$cell}{$sect}{$carr}, 
$cell, $sect, $carr ]]);
}
}
}

for my $record ( sort {
$a-[1] = $b-[1] ||
$a-[2] = $b-[2] ||
$a-[3] = $b-[3] } @data ) {
my( $val, $cell, $sect, $carr, $dist ) = @$record;
print $cell\t $sect\t $carr\t $dist\t $val\n; }




__DATA__
PACE | EVDOPCMD | 33.0 | 101218 | 07 | 
8;1023240136;1218;0;1;00a01a2bcdc7;0310003147702376;ac016d4a;;;5.6.128.8;0;43234169;43234349;;;1;1;1;;0;;19;5.6.128.22;172.30.151.5;304;3;304;3;15;175;15;175;15;175;1;1798;1251;0;0;2;19;20;1;1;1;0;128;5.6.128.8;;;301;5.6.128.8;;;8;304;31;43244037;;;1;18;43234169;01;;43234416;0;0;304;3;21;19;175;15;405;1;1;1;1;0;125;1||
8;1023240137;1218;0;1;00a01db74ace;;ac0174ca;43243423;1678442111;5.6.128.8;1;0;;43242544;43244207;43243423;43243647;;;1000;1;1;;0;;19;5.6.128.26;;372;2;372;2;;43243012;0;43243562;15;175;15;175;15;175;1;5;48;19;20;49;50;;0;1;2;0;68;5.6.128.8;;;301;5.6.128.8;;;8;372;21;43244207;;;1;18;43243423;01;;43242544;0;0;372;2;21;19;175;15;177;3;1;0;0;0;68;1|43243753;0;0;372;2;21;19;175;15;177;3;1;1;1;0;71;1|
8;1023240138;1218;0;1;00a02017ccdb;0310003147833882;aca344d7;;;5.6.128.13;0;43234160;43234358;;;1;1;1;;0;;19;5.6.128.31;172.30.151.5;320;2;320;2;15;75;15;75;15;75;1;2162;1317;0;0;2;19;20;1;1;1;0;104;5.6.128.13;;;306;5.6.128.13;;;8;320;21;43244164;;;1;18;43234160;01;;43234404;0;0;320;2;21;19;75;15;279;6;1;1;1;0;64;1||

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Re: foreach loop

[Jim Gibson]

On 3/24/11 Thu  Mar 24, 2011  9:04 AM, Chris Stinemetz
cstinem...@cricketcommunications.com scribbled:

 I would like $dist be part of the print statement, but I am not sure how to
 code it correctly.

The value of $dist will vary for each row. If you want to print out the
correct value of $dist that corresponds to the value of the sum, then you
will have to store the value.

 
 I am getting the following error:
 
 
 Global symbol @dist requires explicit package name at ./jim.pl line 38.
 Execution of ./banding aborted due to compilation errors.

See note below line 38.

 
 
 
 #!/usr/bin/perl
 
 use warnings;
 use strict;
 
 #my $filepath = 'C:/temp/PCMD';
 # my $filepath = '/home/cstinemetz/perl_programs/1.EVDOPCMD';
 # my $outfile  = 'output.txt';
 
 # open my $fh, '', $filepath or die ERROR opening $filepath: $!;
 # open my $out, '', $outfile or die ERROR opening $outfile: $!;
 
 my %sum;
 
 while (DATA){
 next unless /;/;
 chomp;
 my @data = split /;/;
 my($cell,$sect,$chan,$carr,$rlp1,$rlp2,$rlp3,$rlp4,$dist,$precis) =
   @data[31,32,38,39,44,45,46,47,261,262];
 
 $carr = 
 ( $cell  299  $chan == 175 )  ? 2 :
 ( $chan == 1025 )  ? 2 : 1 ; #nested ternary operator 
 
 $dist = 
 ( length( $dist )  1 ) ? $dist/6.6/8/2*10/10 : 0 ;
  
  
 $sum{$cell}{$sect}{$carr} += $rlp1 += $rlp2 += $rlp3 += $rlp4 || 0 ; }

I see you are changing your program requirements. You are now accumulating
multiple rlp values instead of one.

This line has two problems. The first is that you have placed the closing
brace at the end of the line where it is easy to lose. Perhaps this is why
you have mistakenly used the $dist variable in the lines below, where it is
not in scope. The second problem is the multiple '+=' operators. Do you know
what they will do in this case? I don't. I would have to run a test to see
what the effect is on the intermediate variables. You might be doing more
arithmetic than is necessary.

If you want to accumulate the four variables, why not just do:

$sum{$cell}{$sect}{$carr} += ($rlp1 + $rlp2 + $rlp3 + $rlp4) || 0 ;

 my @data;
 for my $cell ( sort keys %sum ) {
 for my $sect ( sort keys %{$sum{$cell}} ) {
 for my $carr ( sort keys %{$sum{$cell}{$sect}} ) {
 push( @data, [$dist[ $sum{$cell}{$sect}{$carr}, $cell, $sect, $carr ]]);

The syntax $dist[ ... ] tells the Perl parser to access an element of the
array @dist. The proper way to include $dist with the other values would be:

push( @data, [$sum{$cell}{$sect}{$carr}, $cell, $sect, $carr, $dist ] );

but if you use that, you will get a compiler error, as $dist is not in scope
here. You need to store the value of $dist when you read each record, and
retrieve it before using it here.

You will have to figure out how to save and retrieve the value of dist for
each record. There will be one dist value for each record, but the value of
the sum will be the sum of several records, so I think you have inconsistent
logic in what you are trying to do. Which of the several dist values do you
want printed with the sum values?

 }
 }
 }
 
 for my $record ( sort {
 $a-[1] = $b-[1] ||
 $a-[2] = $b-[2] ||
 $a-[3] = $b-[3] } @data ) {
 my( $val, $cell, $sect, $carr, $dist ) = @$record;

This line is good, but you did not store your values this way. See above.



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Re: foreach loop

[John W. Krahn]

Jim Gibson wrote:

On 3/24/11 Thu  Mar 24, 2011  9:04 AM, Chris Stinemetz
cstinem...@cricketcommunications.com  scribbled:



$sum{$cell}{$sect}{$carr} += $rlp1 += $rlp2 += $rlp3 += $rlp4 || 0 ; }


I see you are changing your program requirements. You are now accumulating
multiple rlp values instead of one.

This line has two problems. The first is that you have placed the closing
brace at the end of the line where it is easy to lose. Perhaps this is why
you have mistakenly used the $dist variable in the lines below, where it is
not in scope. The second problem is the multiple '+=' operators. Do you know
what they will do in this case? I don't. I would have to run a test to see
what the effect is on the intermediate variables. You might be doing more
arithmetic than is necessary.


Yes it is.  That is modifying $rlp1, $rlp2 and $rlp3 as well as 
$sum{$cell}{$sect}{$carr}.


And because the = operator is right associative $rlp3 is modified first 
and then $rlp2 and then $rlp1 and finally $sum{$cell}{$sect}{$carr}.


Observe:

$ perl -le'
package JWK;
use Carp;
sub TIESCALAR {
my $class = shift;
my $value = shift || 0;
carp JWK::TIESCALAR got $value;
return bless \$value, $class;
}
sub FETCH {
my $self = shift;
confess wrong type unless ref $self;
croak usage error if @_;
carp JWK::FETCH returned $$self;
return $$self;
}
sub STORE {
my $self = shift;
confess wrong type unless ref $self;
$$self = shift;
carp JWK::STORE set to $$self;
croak usage error if @_;
}
sub DESTROY {
my $self = shift;
confess wrong type unless ref $self;
carp JWK::DESTROY $$self;
}

package main;
tie my $x, JWK, 23;
tie my $y, JWK, 34;
tie my $z, JWK, 45;

my $count = $x + $y + $z;
print \$count = $count;
my $count = $x += $y += $z;
print \$count = $count;
'
JWK::TIESCALAR got 23 at -e line 31
JWK::TIESCALAR got 34 at -e line 32
JWK::TIESCALAR got 45 at -e line 33
JWK::FETCH returned 34 at -e line 35
JWK::FETCH returned 23 at -e line 35
JWK::FETCH returned 45 at -e line 35
$count = 102
JWK::FETCH returned 45 at -e line 37
JWK::FETCH returned 34 at -e line 37
JWK::STORE set to 79 at -e line 37
JWK::FETCH returned 79 at -e line 37
JWK::FETCH returned 23 at -e line 37
JWK::STORE set to 102 at -e line 37
JWK::FETCH returned 102 at -e line 37
$count = 102
JWK::DESTROY 45 at -e line 0
JWK::DESTROY 79 at -e line 0
JWK::DESTROY 102 at -e line 0




John
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Re: foreach loop

[Chris Stinemetz]

Jim,

I am getting really close to finishing up this program. perl is lot's
of fun and I appreciate all your help!

The output is giving me the data I am looking for except for the
following issues:

How would I add the correct code to make sure the array has a numeric
value before the loop iterations begin?

I am getting the following error multiple times and when I look at the
output there are blanks. How can I eliminate this?

Argument  isn't numeric in addition (+) at ./DOband.pl line 30, $fh line 3.

Thank you in advance.

My complete program is posted at the bottom.




 $sum{$cell}{$sect}{$carr} += $rlp1 += $rlp2 += $rlp3 += $rlp4 || 0 ; }


 If you want to accumulate the four variables, why not just do:

 $sum{$cell}{$sect}{$carr} += ($rlp1 + $rlp2 + $rlp3 + $rlp4) || 0 ;


I changed my code to your suggestion. The output is the same, but
yours is much cleaner so I kept yours. Thank you.

#!/usr/bin/perl

use warnings;
use strict;

my $filepath = 'C:/temp/PCMD';
#my $filepath = '/home/cstinemetz/perl_programs/1.EVDOPCMD';
#my $outfile  = 'output.txt';

open my $fh, '', $filepath or die ERROR opening $filepath: $!;
#open my $out, '', $outfile or die ERROR opening $outfile: $!;

my %sum;

while ($fh){
next unless /;/;
chomp;
my @data = split /;/;
my($cell,$sect,$chan,$carr,$rlp1,$rlp2,$rlp3,$rlp4,$dist,$precis) =
  @data[31,32,38,39,44,45,46,47,261,262];

$carr =
( $cell  299  $chan == 175 )  ? 2 :
( $chan == 1025 )   ? 2 : 1 ; #nested ternary 
operator  

$dist = sprintf %.1f,
( length( $dist )  1 ) ? $dist/6.6/8/2*10/10 : 0 ; 

$sum{$cell}{$sect}{$carr}{$dist} += ($rlp1 + $rlp2 + $rlp3 + $rlp4) || 
0 ; }

my @data;
for my $cell ( sort keys %sum ) {
for my $sect ( sort keys %{$sum{$cell}} ) {
for my $carr ( sort keys %{$sum{$cell}{$sect}} 
) {
for my $dist ( sort keys 
%{$sum{$cell}{$sect}{$carr}} ) {
push( @data, [ 
$sum{$cell}{$sect}{$carr}{$dist}, $cell, $sect,
$carr, $dist,]);
}
}
}
}

  for my $record ( sort {
$a-[1] = $b-[1] ||
$a-[2] = $b-[2] ||
$a-[3] = $b-[3] ||
$a-[4] = $b-[4] } @data ) {
my( $val, $cell, $sect, $carr, $dist ) = 
@$record;
print $cell\t $sect\t $carr\t $dist\t $val\n; 
}

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Re: foreach loop

[Rob Dixon]

On 25/03/2011 02:36, Chris Stinemetz wrote:
 Jim,
 
 I am getting really close to finishing up this program. perl is lot's
 of fun and I appreciate all your help!
 
 The output is giving me the data I am looking for except for the
 following issues:
 
 How would I add the correct code to make sure the array has a numeric
 value before the loop iterations begin?
 
 I am getting the following error multiple times and when I look at the
 output there are blanks. How can I eliminate this?
 
 Argument  isn't numeric in addition (+) at ./DOband.pl line 30,$fh  line 
 3.
 
 Thank you in advance.
 
 #!/usr/bin/perl
 
 use warnings;
 use strict;
 
 my $filepath = 'C:/temp/PCMD';
 #my $filepath = '/home/cstinemetz/perl_programs/1.EVDOPCMD';
 #my $outfile  = 'output.txt';
 
 open my $fh, '', $filepath or die ERROR opening $filepath: $!;
 #open my $out, '', $outfile or die ERROR opening $outfile: $!;
 
 my %sum;
 
 while ($fh){
  next unless /;/;
   chomp;
   my @data = split /;/;
   my($cell,$sect,$chan,$carr,$rlp1,$rlp2,$rlp3,$rlp4,$dist,$precis) =
@data[31,32,38,39,44,45,46,47,261,262];
 
   $carr =
   ( $cell  299  $chan == 175 )  ? 2 :
   ( $chan == 1025 )   ? 2 : 1 ; #nested ternary 
 operator  
   
   $dist = sprintf %.1f,
   ( length( $dist )  1 ) ? $dist/6.6/8/2*10/10 : 0 ; 
   
   $sum{$cell}{$sect}{$carr}{$dist} += ($rlp1 + $rlp2 + $rlp3 + $rlp4) || 
 0 ; }
   
   my @data;
   for my $cell ( sort keys %sum ) {
   for my $sect ( sort keys %{$sum{$cell}} ) {
   for my $carr ( sort keys %{$sum{$cell}{$sect}} 
 ) {
   for my $dist ( sort keys 
 %{$sum{$cell}{$sect}{$carr}} ) {
   push( @data, [ 
 $sum{$cell}{$sect}{$carr}{$dist}, $cell, $sect, $carr, $dist,]);
   }
   }
   }
   }
 
for my $record ( sort {
  $a-[1]=  $b-[1] ||
  $a-[2]=  $b-[2] ||
  $a-[3]=  $b-[3] ||
   $a-[4]=  $b-[4] } @data ) {
   my( $val, $cell, $sect, $carr, $dist ) = 
 @$record;
   print $cell\t $sect\t $carr\t $dist\t $val\n; 
 }
 

Your error is because the $rlp variables can sometimes be empty strings
as well as numeric values, in which case they should be skipped over.
Also, since $carr is never used again after being extracted from $data[39], I
would write things this way.

  my ($cell, $sect, $chan, $dist, $precis) = @data[31, 32, 38, 261, 262];

  $dist = sprintf '%.1f', length $dist  1 ? $dist / 6.6 / 8 / 2*10 / 10 : 0; 

  my $carr = ( $cell  299  $chan == 175 ) || $chan == 1025 ? 2 : 1;
  
  for my $i (44..47) {
my $rlp = $data[$i];
$sum{$cell}{$sect}{$carr}{$dist} += $rlp if $rlp;
  }

HTH,

Rob

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RE: foreach loop

[Chris Stinemetz]

Thanks Jim,

I am still unable to sum up the field $rlptxat.

The error I am getting is below:

Scalar found where operator expected at ./jim.pl line 52, near $sum
(Missing semicolon on previous line?)
my variable %sum masks earlier declaration in same scope at ./jim.pl line 54.
my variable %sum masks earlier declaration in same statement at ./jim.pl line 
55.
my variable $cell masks earlier declaration in same statement at ./jim.pl 
line 55.
my variable %sum masks earlier declaration in same scope at ./jim.pl line 56.
my variable $cell masks earlier declaration in same scope at ./jim.pl line 56.
my variable $sect masks earlier declaration in same scope at ./jim.pl line 56.
my variable %sum masks earlier declaration in same scope at ./jim.pl line 58.
my variable $cell masks earlier declaration in same scope at ./jim.pl line 58.
my variable $sect masks earlier declaration in same scope at ./jim.pl line 58.
my variable $chan masks earlier declaration in same scope at ./jim.pl line 58.
syntax error at ./jim.pl line 52, near $sum
Global symbol %sum requires explicit package name at ./jim.pl line 52.
Global symbol $cell requires explicit package name at ./jim.pl line 52.
Global symbol $sect requires explicit package name at ./jim.pl line 52.
Global symbol $chan requires explicit package name at ./jim.pl line 52.
Global symbol $rlptxat requires explicit package name at ./jim.pl line 54.
Execution of ./jim.pl aborted due to compilation errors.

My code is as follows:

#!/usr/bin/perl

use warnings;
use strict;

my @records = ();

while (DATA){

next unless /;/;
chomp;
my @data = split /;/;
my($cell,$sect,$chan,$carr,$rlptxat1,$dist,$precis) = 
@data[31,32,38,39,44,261,262];

$carr =
( $chan == 75 )   ? 2 :
( $chan == 1025 ) ? 2 : 1 ; #nested ternary operator

$dist =
( length( $dist )  1 ) ? $dist/6.6/8/2*10/10 : '' ;

push @records, {
cell= $cell,
sect= $sect,
carr= $carr,
chan= $chan,
RTD = $dist,
RLP1= $rlptxat1,
Precis  = $precis,
};
}

my @sorted = sort {
$a-{cell} = $b-{cell} ||
$a-{sect} = $b-{sect} ||
$a-{carr} = $b-{carr}
  } @records ;

my %sum

$sum{$cell}{$sect}{$chan} += $rlptxat

for my $cell ( sort keys %sum ) {
for my $sect ( sort keys %{$sum{$cell}} ) {
for my $chan ( sort keys %{$sum{$cell}{$sect}} ) {
print Value of sum($cell,$sect,$chan) is  .
$sum{$cell}{$sect}{$chan} . \n;
}
}
}

__DATA__
PACE | EVDOPCMD | 33.0 | 101218 | 07 |
8;1023240136;1218;0;1;00a01a2bcdc7;0310003147702376;ac016d4a;;;5.6.128.8;0;43234169;43234349;;;1;1;1;;0;;19;5.6.128.22;172.30.151.5;304;3;304;3;15;175;15;175;15;175;1;1798;1251;0;0;2;19;20;1;1;1;0;128;5.6.128.8;;;301;5.6.128.8;;;8;304;31;43244037;;;1;18;43234169;01;;43234416;0;0;304;3;21;19;175;15;405;1;1;1;1;0;125;1||
8;1023240137;1218;0;1;00a01db74ace;;ac0174ca;43243423;1678442111;5.6.128.8;1;0;;43242544;43244207;43243423;43243647;;;1000;1;1;;0;;19;5.6.128.26;;372;2;372;2;;43243012;0;43243562;15;175;15;175;15;175;1;5;48;19;20;49;50;;0;1;2;0;68;5.6.128.8;;;301;5.6.128.8;;;8;372;21;43244207;;;1;18;43243423;01;;43242544;0;0;372;2;21;19;175;15;177;3;1;0;0;0;68;1|43243753;0;0;372;2;21;19;175;15;177;3;1;1;1;0;71;1|
8;1023240138;1218;0;1;00a02017ccdb;0310003147833882;aca344d7;;;5.6.128.13;0;43234160;43234358;;;1;1;1;;0;;19;5.6.128.31;172.30.151.5;320;2;320;2;15;75;15;75;15;75;1;2162;1317;0;0;2;19;20;1;1;1;0;104;5.6.128.13;;;306;5.6.128.13;;;8;320;21;43244164;;;1;18;43234160;01;;43234404;0;0;320;2;21;19;75;15;279;6;1;1;1;0;64;1||

Re: foreach loop

[Jim Gibson]

On 3/23/11 Wed  Mar 23, 2011  10:02 AM, Chris Stinemetz
cstinem...@cricketcommunications.com scribbled:

 Thanks Jim,
 
 I am still unable to sum up the field $rlptxat.
 
 The error I am getting is below:
 
 Scalar found where operator expected at ./jim.pl line 52, near $sum
 (Missing semicolon on previous line?)



 my %sum

The above line needs a semicolon.

Please reduce the size of your posts. Maybe shorten the data by including
fewer rows and columns. The concepts will still be the same. Thanks.



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Re: foreach loop

[Chas. Owens]

On Mon, Mar 21, 2011 at 01:46, Mike McClain m.d.mccl...@cox.net wrote:
snip
  my @report = map
  $_-{cell}\t$_-{sect}\t$_-{carr}\t$_-{chan}\t$_-{dist}\n , @sorted;
  print @report ;

 This map will consume a lot of memory, better do it using a foreach loop.

 In what way will the use of map here use any more memory than a foreach loop?
snip

The problem is that map returns a list.  That list will exist in
memory as you copy it to @report.  Just before the assignment is
finished, you will be using twice the amount of memory you expect.
Perl doesn't tend to return memory to the system, so, even though no
variable is using it, the memory used to hold the list will still be
held by perl.  Happily, perl will reuse the memory, so, as long as it
isn't huge, it normally isn't a big deal.



-- 
Chas. Owens
wonkden.net
The most important skill a programmer can have is the ability to read.

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Re: foreach loop

[Jim Gibson]

On 3/23/11 Wed  Mar 23, 2011  10:02 AM, Chris Stinemetz
cstinem...@cricketcommunications.com scribbled:

In addition to the missing semicolon, the declaration of %sum must appear
before it is used, i.e. before the while(DATA) loop. The line adding
values of $rlptxat1 to the sum must appear inside the while loop, not after
it.

Run this program on your data:

#!/usr/local/bin/perl

use warnings;
use strict;

my %sum;
while (DATA){

  next unless /;/;
  chomp;
  my @data = split /;/;
  my($cell,$sect,$chan,$carr,$rlptxat1,$dist,$precis) =
  @data[31,32,38,39,44,261,262];

  $sum{$cell}{$sect}{$chan} += $rlptxat1 || 0;
}

for my $cell ( sort keys %sum ) {
  for my $sect ( sort keys %{$sum{$cell}} ) {
for my $chan ( sort keys %{$sum{$cell}{$sect}} ) {
  print Value of sum($cell,$sect,$chan) is  .
$sum{$cell}{$sect}{$chan} . \n;
}
  }
}



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RE: foreach loop

[Chris Stinemetz]

That worked! Thanks Jim.

Chris

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RE: foreach loop

[Chris Stinemetz]

Jim,

I have another question.

How do I sort the results so it is from smallest to largest starting with 
$cell,$sect,$carr?

Thanks again for all you help. I am gaining a much better understanding.

This is what I got:

#!/usr/bin/perl

use warnings;
use strict;


#my $filepath = 'C:/temp/PCMD';
#my $filepath = 'C:/cygwin/home/cstinemetz/perl_programs/1.EVDOPCMD';
# my $outfile  = 'output.txt';

#open my $fh, '', $filepath or die ERROR opening $filepath: $!;
# open my $out, '', $outfile or die ERROR opening $outfile: $!;

my %sum;
#my @records = ();

while (DATA){

next unless /;/;
chomp;
my @data = split /;/;

my($cell,$sect,$chan,$carr,$rlptxat1,$rlptxat2,$rlptxat3,$rlptxat4,$dist,$precis)
 = @data[31,32,38,39,44,45,46,47,261,262];

$carr = 
( $chan == 75 )   ? 2 : 
( $chan == 1025 ) ? 2 : 1 ; #nested ternary operator

$dist = 
( length( $dist )  1 ) ? $dist/6.6/8/2*10/10 : 0 ;


$sum{$cell}{$sect}{$carr}{$dist} += $rlptxat1 += $rlptxat2 += $rlptxat3 
+= $rlptxat4 || 0 ; }

for my $cell ( sort keys %sum ) {
for my $sect ( sort keys %{$sum{$cell}} ) {
for my $carr ( sort keys %{$sum{$cell}{$sect}} ) {
for my $dist ( sort keys 
%{$sum{$cell}{$sect}{$carr}} ) {
print $cell\t $sect\t $carr\t $dist\t .
$sum{$cell}{$sect}{$carr}{$dist} . \n;
}
}
}
}

And this is the current output:

10   2   1   0.710227272727273  439
100  1   1   0  469
100  2   1   0  3207
101  3   1   0  96
102  3   1   0  1623
107  1   1   0  48
109  2   1   0  49
11   2   1   0  48
110  3   1   0.681818181818182  49
114  3   1   0  48
121  2   1   2.78409090909091   3628


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Re: foreach loop

[Jim Gibson]

On 3/23/11 Wed  Mar 23, 2011  12:49 PM, Chris Stinemetz
cstinem...@cricketcommunications.com scribbled:

 Jim,
 
 I have another question.
 
 How do I sort the results so it is from smallest to largest starting with
 $cell,$sect,$carr?

It is difficult to sort a multi-level, nested hash. I would transfer the
values to an array-of-arrays and sort that:

#!/usr/local/bin/perl

use warnings;
use strict;

my %sum;
while (DATA){
next unless /;/;
  chomp;
  my @data = split /;/;
  my($cell,$sect,$chan,$carr,$rlptxat1,$dist,$precis) =
  @data[31,32,38,39,44,261,262];
  $sum{$cell}{$sect}{$chan} += $rlptxat1 || 0;
}

my @data;
for my $cell ( sort keys %sum ) {
  for my $sect ( sort keys %{$sum{$cell}} ) {
for my $chan ( sort keys %{$sum{$cell}{$sect}} ) {
  push( @data, [ $sum{$cell}{$sect}{$chan}, $cell, $sect, $chan ]);
}
  }
}

for my $record ( sort { $a-[0] = $b-[0] } @data ) {
my( $val, $cell, $sect, $chan ) = @$record;
print The value of ($cell,$sect,$chan) is $val\n;
}



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RE: foreach loop

[Chris Stinemetz]

No, it doesn't. What is a rlptxat element? Where do they come from.

rlptxat is just an element indexed at 44 that has a value, in which I would 
like to sum up, when it has the same elements cell sect and carr in the 
record.

I hope this helps

Thank you,

Chris 

At 8:03 PM -0600 3/20/11, Chris Stinemetz wrote:
Jim,

Thanks for your feedback. I am actually trying to sum up all rlptxat 
elements that have the same cell, sect, and chan elements in the 
array. I hope this clarifies.

No, it doesn't. What is a rlptxat element? Where do they come from.

You can define a multiple-level hash with three nested keys (cell, 
sect, chan) to hold the sum of all elements with the same key values 
(a triple):

   my %sum;

Find values of cell, sect, and chan:

$cell = ?
$sect = ?
$chan = ?

Add the value with these keys to the sum:

   $sum{$cell}{$sect}{$chan} += ?

Iterate over the result:

   for my $cell ( sort keys %sum ) {
 for my $sect ( sort keys %{$sum{$cell}} ) {
   for my $chan ( sort keys %{$sum{$cell}{$sect}} ) {
   print Value of sum($cell,$sect,$chan) is 
$sum{$cell}{$sect}{$chan}\n;
   }
 }
   }

Good luck!

-- 
Jim Gibson
j...@gibson.org

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Re: foreach loop

[Jim Gibson]

On 3/22/11 Tue  Mar 22, 2011  2:24 PM, Chris Stinemetz
cstinem...@cricketcommunications.com scribbled:

 No, it doesn't. What is a rlptxat element? Where do they come from.
 
 rlptxat is just an element indexed at 44 that has a value, in which I would
 like to sum up, when it has the same elements cell sect and carr in the
 record.

OK. With this information and that from previous posts, your requirements
may be summaryized as follows:

You have a file with one record per line, each line consisting of a number
of fields. Within each record may be found values of cell, sect, carr, and
rlptxat at fixed column positions (e.g. 44 for rlptxat). You with to sum up
the values of the rlptxat field for all records having the same values of
cell, sect, and carr.

Correct?

 At 8:03 PM -0600 3/20/11, Chris Stinemetz wrote:
 Jim,
 
 Thanks for your feedback. I am actually trying to sum up all rlptxat
 elements that have the same cell, sect, and chan elements in the
 array. I hope this clarifies.
 
 No, it doesn't. What is a rlptxat element? Where do they come from.
 
 You can define a multiple-level hash with three nested keys (cell,
 sect, chan) to hold the sum of all elements with the same key values
 (a triple):
 
my %sum;
 
 Find values of cell, sect, and chan:

Let @record be the array containing the values from each row, as returned by
the split function, for example. Then:

 
my $cell = $record[?] # ? is column number for cell field
my $sect = $record[?] # ? is column number for sect field
my $chan = $record[?] # ? is column number for chan field
my $rlptxat = $record[44];

Or more succintly:

my( $cell, $sect, $chan, $rlptxat ) = @record[ ?, ?, ?, 44 ]; # ? as above

 
 Add the value with these keys to the sum:
 
$sum{$cell}{$sect}{$chan} += $rlptxat

 
 Iterate over the result:
 

   for my $cell ( sort keys %sum ) {
 for my $sect ( sort keys %{$sum{$cell}} ) {
   for my $chan ( sort keys %{$sum{$cell}{$sect}} ) {
   print Value of sum($cell,$sect,$chan) is  .
 $sum{$cell}{$sect}{$chan} . \n;
   }
 }
   }

And you are done.



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RE: foreach loop

[Chris Stinemetz]

Jim,

You hit it right on. This is exactly what I am trying to do.

 OK. With this information and that from previous posts, your requirements may 
 be summaryized as follows:

 You have a file with one record per line, each line consisting of a number of 
 fields. Within each record may be found values of cell, sect, carr, and 
 rlptxat at fixed
 column positions (e.g. 44 for rlptxat). You with to sum up the values of the 
 rlptxat field for all records having the same values of cell, sect, and carr.

 Correct?

I took your advice but I am still unable to get the results I want.

Below is what I have with your code added. I also changed it from $fh to DATA 
so you can get an idea of the input data
and copy and paste it if you need to.

Thanks for a all your help!

Chris

#!/usr/bin/perl

use warnings;
use strict;


#my $filepath = 'C:/temp/PCMD';
#my $filepath = 'C:/cygwin/home/cstinemetz/perl_programs/1.EVDOPCMD';
#my $outfile  = 'output.txt';

#open my $fh, '', $filepath or die ERROR opening $filepath: $!;
#open my $out, '', $outfile or die ERROR opening $outfile: $!;

my @records = ();

while (DATA){

next unless /;/;
chomp;
my @data = split /;/;
my($cell,$sect,$chan,$carr,$rlptxat,$dist,$precis) = 
@data[31,32,38,39,44,261,262];

# my %sum

# $sum{$cell}{$sect}{$chan} += $rlptxat

# for my $cell ( sort keys %sum ) {
# for my $sect ( sort keys %{$sum{$cell}} ) {
# for my $chan ( sort keys %{$sum{$cell}{$sect}} ) {
# print Value of sum($cell,$sect,$chan) is  .
# $sum{$cell}{$sect}{$chan} . \n;
# }
# }
# }



$carr =
( $chan == 75 )   ? 2 :
( $chan == 1025 ) ? 2 : 1 ; #nested ternary operator

$dist =
( length( $dist )  1 ) ? $dist/6.6/8/2*10/10 : '' ;


push @records, {
cell   = $cell,
sect   = $sect,
carr   = $carr,
chan   = $chan,
RTD= $dist,
Precis = $precis,
};
}

my @sorted = sort {
$a-{cell} = $b-{cell} ||
$a-{sect} = $b-{sect} ||
$a-{carr} = $b-{carr}
  } @records ;


for my $tuple ( @sorted ){
#print sprintf(%15s\t%10s\t%10s\n,$tuple-{cell}\t $tuple-{sect}\t 
$tuple-{carr});
print $tuple-{cell}\t $tuple-{sect}\t $tuple-{carr}\t $tuple-{chan}\t 
$tuple-{RTD}\n;
}
# for my $tuple ( @sorted ){
# print $out $tuple-{cell} $tuple-{sect} $tuple-{carr} $tuple-{RTD}\n;
# }
# close $out;


__DATA__
PACE | EVDOPCMD | 33.0 | 101218 | 07 |
8;1023240136;1218;0;1;00a01a2bcdc7;0310003147702376;ac016d4a;;;5.6.128.8;0;43234169;43234349;;;1;1;1;;0;;19;5.6.128.22;172.30.151.5;304;3;304;3;15;175;15;175;15;175;1;1798;1251;0;0;2;19;20;1;1;1;0;128;5.6.128.8;;;301;5.6.128.8;;;8;304;31;43244037;;;1;18;43234169;01;;43234416;0;0;304;3;21;19;175;15;405;1;1;1;1;0;125;1||
8;1023240137;1218;0;1;00a01db74ace;;ac0174ca;43243423;1678442111;5.6.128.8;1;0;;43242544;43244207;43243423;43243647;;;1000;1;1;;0;;19;5.6.128.26;;372;2;372;2;;43243012;0;43243562;15;175;15;175;15;175;1;5;48;19;20;49;50;;0;1;2;0;68;5.6.128.8;;;301;5.6.128.8;;;8;372;21;43244207;;;1;18;43243423;01;;43242544;0;0;372;2;21;19;175;15;177;3;1;0;0;0;68;1|43243753;0;0;372;2;21;19;175;15;177;3;1;1;1;0;71;1|
8;1023240138;1218;0;1;00a02017ccdb;0310003147833882;aca344d7;;;5.6.128.13;0;43234160;43234358;;;1;1;1;;0;;19;5.6.128.31;172.30.151.5;320;2;320;2;15;75;15;75;15;75;1;2162;1317;0;0;2;19;20;1;1;1;0;104;5.6.128.13;;;306;5.6.128.13;;;8;320;21;43244164;;;1;18;43234160;01;;43234404;0;0;320;2;21;19;75;15;279;6;1;1;1;0;64;1||

RE: foreach loop

[Jim Gibson]

At 9:58 PM -0600 3/22/11, Chris Stinemetz wrote:

Jim,

You hit it right on. This is exactly what I am trying to do.

 OK. With this information and that from previous posts, your 
requirements may be summaryized as follows:


 You have a file with one record per line, each line consisting of 
a number of fields. Within each record may be found values of cell, 
sect, carr, and rlptxat at fixed
 column positions (e.g. 44 for rlptxat). You with to sum up the 
values of the rlptxat field for all records having the same values 
of cell, sect, and carr.



 Correct?


I took your advice but I am still unable to get the results I want.

Below is what I have with your code added. I also changed it from 
$fh to DATA so you can get an idea of the input data

and copy and paste it if you need to.



But you commented out my code, and deleted the part that prints the 
results. Your code does not sum anything. You don't need to sort the 
records to produce a sum.


Run your data through my code and see what you get. Then explain why 
it does not do what you want.


--
Jim Gibson
j...@gibson.org

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Re: foreach loop

[Mike McClain]

On Sun, Mar 20, 2011 at 10:06:25AM +0200, Shlomi Fish wrote:
 On Sunday 20 Mar 2011 05:43:38 Chris Stinemetz wrote:
  I am trying to code a foreach loop, that will add all occurrences of the
  element rlptxat that have the same elements cell, sect and chan.
snip 
  $record{dist}/6.6/8/2*10/10 : '' ;

Chris take this much of this calculation '6.6/8/2*10/10' outside the loop
and precalculate the constant portion then inside the loop only calculate
$record{dist}*$your_constant

  my @report = map
  $_-{cell}\t$_-{sect}\t$_-{carr}\t$_-{chan}\t$_-{dist}\n , @sorted;
  print @report ;
 
 This map will consume a lot of memory, better do it using a foreach loop.

In what way will the use of map here use any more memory than a foreach loop?

Thanks,
Mike
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Re: foreach loop

[Shlomi Fish]

Hi Chris,

On Sunday 20 Mar 2011 05:43:38 Chris Stinemetz wrote:
 I am trying to code a foreach loop, that will add all occurrences of the
 element rlptxat that have the same elements cell, sect and chan.
 
 My failed attempt can be located in between the ### lines.
 

If I understand your code correctly, then you should somehow serialise those 
into the same hash key (possibly using Storable.pm/JSON/etc.). Don't use the 
old $my_hash{$key1, $key2, $key3} notation. You may also opt to construct a 
hash of hashes.

Now a few other comments:

 Below is what I have so far.
 
 Thank you in advance,
 Chris
 
 #!/usr/bin/perl
 
 use warnings;
 use strict;
 use File::Slurp;
 my $filepath = 'C:/temp/PCMD';
 my $output  = 'output.txt';
 

You should add some empty lines here:

http://perl-begin.org/tutorials/bad-elements/#paragraphs

 my %cols = (
   cell= 31,
   sect= 32,
   chan= 38,
   dist= 261,
   precis  = 262,
   rlptxat = 44,
 );
 
 my @records;
 
 my @lines = read_file( $filepath );
 
 chomp @lines;
 

You should read the file line-by-line, using:

 $fh 

Not slurp it.

 foreach my $line ( @lines ) {
 
   next unless $line =~ /;/;
   my %record;
 # this gets just what you want into a hash using a hash slice and an #
 array slice. # the order of keys and values will be the same for any #
 given hash
 
   @record{ keys %cols } = (split /;/, $line)[ values %cols ];
 
 
 
   $record{rlptxat} = ( length($record{rlptxat}) 1 ) ?
 $record{rlptxat}{cell, sect, chan, dist}++ : '' ;
 
 
 
   $record{carr} =
   ( $record{chan} == 75 )   ? 2 :
   ( $record{chan} == 1025 ) ? 2 : 1 ;
   #1; # 
Common carrier
   $record{dist} = ( length( $record{dist})  1 ) ?
 $record{dist}/6.6/8/2*10/10 : '' ;
 
   push( @records, \%record ) ;
 }
 
 my @sorted = sort {
   $a-{cell} = $b-{cell} ||
   $a-{sect} = $b-{sect} ||
   $a-{carr} = $b-{carr}
   } @records ;
 
 my @report = map
 $_-{cell}\t$_-{sect}\t$_-{carr}\t$_-{chan}\t$_-{dist}\n , @sorted;
 
 
 
 print @report ;

This map will consume a lot of memory, better do it using a foreach loop.

Regards,

Shlomi Fish

 write_file($output, @report) ;

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Re: foreach loop

[Uri Guttman]

 SF == Shlomi Fish shlo...@iglu.org.il writes:

   my @records;
   
   my @lines = read_file( $filepath );
   
   chomp @lines;
   

  SF You should read the file line-by-line, using:

  SF$fh 

  SF Not slurp it.

there is no reason to read it line by line. it is small enough to
slurp. slurping is faster and generally cleaner than line by
line. considering he was doing a poor version of slurping before, this
is much better.

   print @report ;

  SF This map will consume a lot of memory, better do it using a foreach loop.

again, not. his file isn't that large. given he wants to print to stdout
and also a file, it is easier to build up the report one time and print
twice. simple and also faster.

uri

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RE: foreach loop

[Chris Stinemetz]

So back to the question. How can I nest this foreach loop correctly to add all 
occurrences of the element rlptxat that have the same elements cell, sect and 
chan in the array?

$record{rlptxat} = ( length($record{rlptxat}) 1 ) ? $record{rlptxat}{cell, 
sect, chan, dist}++ : '' ;

Thank you very much.

Chris

#!/usr/bin/perl

use warnings;
use strict;
use File::Slurp;
my $filepath = 'C:/temp/PCMD';
my $output  = 'output.txt';

my %cols = (
cell= 31,
sect= 32,
chan= 38,
dist= 261,
precis  = 262,
rlptxat = 44,
);

my @records;

my @lines = read_file( $filepath );

chomp @lines;

foreach my $line ( @lines ) {

next unless $line =~ /;/;
my %record;
# this gets just what you want into a hash using a hash slice and an array 
slice. 
# the order of keys and values will be the same for any # given hash

@record{ keys %cols } = (split /;/, $line)[ values %cols ]; 



$record{rlptxat} = ( length($record{rlptxat}) 1 ) ? 
$record{rlptxat}{cell, sect, chan, dist}++ : '' ;



$record{carr} =
( $record{chan} == 75 )   ? 2 :
( $record{chan} == 1025 ) ? 2 : 1 ;
#1; # 
Common carrier
$record{dist} = ( length( $record{dist})  1 ) ? 
$record{dist}/6.6/8/2*10/10 : '' ;

push( @records, \%record ) ;
}

my @sorted = sort {
$a-{cell} = $b-{cell} ||
$a-{sect} = $b-{sect} ||
$a-{carr} = $b-{carr}
} @records ;

my @report = map $_-{cell}\t$_-{sect}\t$_-{carr}\t$_-{chan}\t$_-{dist}\n 
, @sorted;



print @report ;
write_file($output, @report) ;


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RE: foreach loop

[Jim Gibson]

At 8:31 AM -0600 3/20/11, Chris Stinemetz wrote:
So back to the question. How can I nest this foreach loop correctly 
to add all occurrences of the element rlptxat that have the same 
elements cell, sect and chan in the array?


$record{rlptxat} = ( length($record{rlptxat}) 1 ) ? 
$record{rlptxat}{cell, sect, chan, dist}++ : '' ;


That doesn't compile on my system under 'use strict:' because cell, 
sect, chan, dist are barewords, i.e. not variables or strings. They 
will look more like parameterless functions to the Perl interpreter. 
While they are allowed in some circumstances under 'strict', this is 
not one of them.


You should make them explicitly strings, either as ('cell', 'sect', 
'chan', 'dist') or as qw( cell sect chan dist) (note the absence of 
commas in the second version.


Since you are assigning a hash slice, which has multiple values, you 
should use @record{...} instead of $record{...}, which is a single, 
scalar value:


@record{rlptxat} = ( length($record{rlptxat}) 1 ) ? 
@record{rlptxat}{ qw(cell sect chan dist)}++ : '' ;


However, it is not clear what you are trying to do. The rlptxat 
element is the 45th field on the input line. Are you trying to 
replace that element with a reference to a hash containing 4 elements 
from elsewhere in the line? Or are you trying to increment the values 
in those other 4 elements.


Try writing multiple lines to do what you want. Don't try to stuff 
everything into one line until you know Perl better. If you write a 
bunch of lines to do something, people here will gladly tell you how 
you could have done it in fewer lines.


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Jim Gibson
j...@gibson.org

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RE: foreach loop

[Chris Stinemetz]

Jim,

Thanks for your feedback. I am actually trying to sum up all rlptxat elements 
that have the same cell, sect, and chan elements in the array. I hope this 
clarifies.

Thank you,

Chris 

-Original Message-
From: Jim Gibson [mailto:jimsgib...@gmail.com] 
Sent: Sunday, March 20, 2011 5:58 PM
To: beginners@perl.org
Subject: RE: foreach loop

At 8:31 AM -0600 3/20/11, Chris Stinemetz wrote:
So back to the question. How can I nest this foreach loop correctly 
to add all occurrences of the element rlptxat that have the same 
elements cell, sect and chan in the array?

$record{rlptxat} = ( length($record{rlptxat}) 1 ) ? 
$record{rlptxat}{cell, sect, chan, dist}++ : '' ;

That doesn't compile on my system under 'use strict:' because cell, 
sect, chan, dist are barewords, i.e. not variables or strings. They 
will look more like parameterless functions to the Perl interpreter. 
While they are allowed in some circumstances under 'strict', this is 
not one of them.

You should make them explicitly strings, either as ('cell', 'sect', 
'chan', 'dist') or as qw( cell sect chan dist) (note the absence of 
commas in the second version.

Since you are assigning a hash slice, which has multiple values, you 
should use @record{...} instead of $record{...}, which is a single, 
scalar value:

@record{rlptxat} = ( length($record{rlptxat}) 1 ) ? 
@record{rlptxat}{ qw(cell sect chan dist)}++ : '' ;

However, it is not clear what you are trying to do. The rlptxat 
element is the 45th field on the input line. Are you trying to 
replace that element with a reference to a hash containing 4 elements 
from elsewhere in the line? Or are you trying to increment the values 
in those other 4 elements.

Try writing multiple lines to do what you want. Don't try to stuff 
everything into one line until you know Perl better. If you write a 
bunch of lines to do something, people here will gladly tell you how 
you could have done it in fewer lines.

-- 
Jim Gibson
j...@gibson.org

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RE: foreach loop

[Jim Gibson]

At 8:03 PM -0600 3/20/11, Chris Stinemetz wrote:

Jim,

Thanks for your feedback. I am actually trying to sum up all rlptxat 
elements that have the same cell, sect, and chan elements in the 
array. I hope this clarifies.


No, it doesn't. What is a rlptxat element? Where do they come from.

You can define a multiple-level hash with three nested keys (cell, 
sect, chan) to hold the sum of all elements with the same key values 
(a triple):


  my %sum;

Find values of cell, sect, and chan:

$cell = ?
$sect = ?
$chan = ?

Add the value with these keys to the sum:

  $sum{$cell}{$sect}{$chan} += ?

Iterate over the result:

  for my $cell ( sort keys %sum ) {
for my $sect ( sort keys %{$sum{$cell}} ) {
  for my $chan ( sort keys %{$sum{$cell}{$sect}} ) {
  print Value of sum($cell,$sect,$chan) is 
$sum{$cell}{$sect}{$chan}\n;

  }
}
  }

Good luck!

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j...@gibson.org

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Re: foreach loop

[terry]

于 2011-3-21 13:33, Jim Gibson 写道:

Iterate over the result:

   for my $cell ( sort keys %sum ) {
 for my $sect ( sort keys %{$sum{$cell}} ) {
   for my $chan ( sort keys %{$sum{$cell}{$sect}} ) {
   print Value of sum($cell,$sect,$chan) is
$sum{$cell}{$sect}{$chan}\n;
   }
 }
   }



And Data::Dumper could help you find out the complicated data structure.

terry.

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foreach loop

[Chris Stinemetz]

I am trying to code a foreach loop, that will add all occurrences of the 
element rlptxat that have the same elements cell, sect and chan.

My failed attempt can be located in between the ### lines.

Below is what I have so far.

Thank you in advance,
Chris 

#!/usr/bin/perl

use warnings;
use strict;
use File::Slurp;
my $filepath = 'C:/temp/PCMD';
my $output  = 'output.txt';

my %cols = (
cell= 31,
sect= 32,
chan= 38,
dist= 261,
precis  = 262,
rlptxat = 44,
);

my @records;

my @lines = read_file( $filepath );

chomp @lines;

foreach my $line ( @lines ) {

next unless $line =~ /;/;
my %record;
# this gets just what you want into a hash using a hash slice and an # array 
slice. 
# the order of keys and values will be the same for any # given hash

@record{ keys %cols } = (split /;/, $line)[ values %cols ];



$record{rlptxat} = ( length($record{rlptxat}) 1 ) ? 
$record{rlptxat}{cell, sect, chan, dist}++ : '' ;



$record{carr} =
( $record{chan} == 75 )   ? 2 :
( $record{chan} == 1025 ) ? 2 : 1 ;
#1; # 
Common carrier
$record{dist} = ( length( $record{dist})  1 ) ? 
$record{dist}/6.6/8/2*10/10 : '' ;

push( @records, \%record ) ;
}

my @sorted = sort {
$a-{cell} = $b-{cell} ||
$a-{sect} = $b-{sect} ||
$a-{carr} = $b-{carr}
} @records ;

my @report = map $_-{cell}\t$_-{sect}\t$_-{carr}\t$_-{chan}\t$_-{dist}\n 
, @sorted;



print @report ;
write_file($output, @report) ;

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Problem with foreach loop

[HACKER Nora]

Hello list,

Could someone please explain why this test script:

my @arr1 = qw(one two three);
my @arr2 = qw(1 2 3);

foreach my $arr1 ( @arr1 ) {
print Arr1: $arr1\n;
foreach my $arr2 ( @arr2 ) {
print Arr2: $arr2\n;
if ( $arr2 eq '2' ) {
shift @arr1;
}
}
}

produces that result:

oracle:/opt/data/magna/wartung/work/nora ./test.pl
Arr1: one
Arr2: 1
Arr2: 2
Arr2: 3
Arr1: three
Arr2: 1
Arr2: 2
Arr2: 3

whereas I had expected the output to be like this:

oracle:/opt/data/magna/wartung/work/nora ./test.pl
Arr1: one
Arr2: 1
Arr2: 2
Arr2: 3
Arr1: two   # why not?
Arr2: 1 # why not?
Arr2: 2 # why not?
Arr1: three
Arr2: 1
Arr2: 2
Arr2: 3

Thanks in advance!

Regards, 
Nora 

WG: Problem with foreach loop

[HACKER Nora]

Sorry, cp-accident...

The proper result should be of course:

oracle:/opt/data/magna/wartung/work/nora ./test.pl
Arr1: one
Arr2: 1
Arr2: 2
Arr1: two
Arr2: 1
Arr2: 2
Arr1: three
Arr2: 1
Arr2: 2

Regards, 
Nora 



 -Ursprüngliche Nachricht-
 Von: HACKER Nora
 Gesendet: Montag, 27. September 2010 09:20
 An: beginners@perl.org
 Betreff: Problem with foreach loop
 
 Hello list,
 
 Could someone please explain why this test script:
 
 my @arr1 = qw(one two three);
 my @arr2 = qw(1 2 3);
 
 foreach my $arr1 ( @arr1 ) {
 print Arr1: $arr1\n;
 foreach my $arr2 ( @arr2 ) {
 print Arr2: $arr2\n;
 if ( $arr2 eq '2' ) {
 shift @arr1;
 }
 }
 }
 
 produces that result:
 
 oracle:/opt/data/magna/wartung/work/nora ./test.pl
 Arr1: one
 Arr2: 1
 Arr2: 2
 Arr2: 3
 Arr1: three
 Arr2: 1
 Arr2: 2
 Arr2: 3
 
 whereas I had expected the output to be like this:
 
 oracle:/opt/data/magna/wartung/work/nora ./test.pl
 Arr1: one
 Arr2: 1
 Arr2: 2
 Arr2: 3
 Arr1: two # why not?
 Arr2: 1   # why not?
 Arr2: 2   # why not?
 Arr1: three
 Arr2: 1
 Arr2: 2
 Arr2: 3
 
 Thanks in advance!
 
 Regards,
 Nora
 
 


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Re: Problem with foreach loop

[Shlomi Fish]

Hi Nora,

On Monday 27 September 2010 09:19:46 HACKER Nora wrote:
 Hello list,
 
 Could someone please explain why this test script:
 
 my @arr1 = qw(one two three);
 my @arr2 = qw(1 2 3);
 
 foreach my $arr1 ( @arr1 ) {
 print Arr1: $arr1\n;
 foreach my $arr2 ( @arr2 ) {
 print Arr2: $arr2\n;
 if ( $arr2 eq '2' ) {
 shift @arr1;

You shouldn't modify an array (@arr1 in this case) while iterating over it 
using foreach. Otherwise, the results will be unpredictable. One option to 
overcome it is to do:

[code]
my @arr1_copy = @arr1;

while (defined (my $arr1_elem = shift(@arr1_copy)))
{
# Do something with $arr1_elem
}
[/code]

This will not work properly if @arr1 contains undef elements but it's 
relatively easy to fix:

[code]
while (@arr1_copy)
{
my $arr1_elem = shift;
}
[/code]

Regards,

Shlomi Fish

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AW: Problem with foreach loop

[HACKER Nora]

Hi Michael,

 

Thanks for your fast reply. I didn't realize that the shift is of
immediate effect not only to the array but also to the current element
of iteration in the loop itself.

 

LG, 
Nora 

 

 

Von: Michael Newman [mailto:newman.michae...@gmail.com] 
Gesendet: Montag, 27. September 2010 09:34
An: HACKER Nora
Betreff: Re: Problem with foreach loop

 

When $arr2 eq '2', you shift  'one' off @arr1, but you're still working
with$ arr[0], which is now 'two'.  When the second foreach ends, it
moves onto $arr1[1], which is 'three'.

Also, if you want it to stop at '2', put a last; after you shift from
@arr1.

On Sep 27, 2010 3:22 AM, HACKER Nora nora.hac...@stgkk.at
wrote:

Hello list,

Could someone please explain why this test script:

my @arr1 = qw(one two three);
my @arr2 = qw(1 2 3);

foreach my $arr1 ( @arr1 ) {
   print Arr1: $arr1\n;
   foreach my $arr2 ( @arr2 ) {
   print Arr2: $arr2\n;
   if ( $arr2 eq '2' ) {
   shift @arr1;
   }
   }
}

produces that result:

oracle:/opt/data/magna/wartung/work/nora ./test.pl
Arr1: one
Arr2: 1
Arr2: 2
Arr2: 3
Arr1: three
Arr2: 1
Arr2: 2
Arr2: 3

whereas I had expected the output to be like this:

oracle:/opt/data/magna/wartung/work/nora ./test.pl
Arr1: one
Arr2: 1
Arr2: 2
Arr2: 3
Arr1: two   # why not?
Arr2: 1 # why not?
Arr2: 2 # why not?
Arr1: three
Arr2: 1
Arr2: 2
Arr2: 3

Thanks in advance!

Regards,
Nora

Re: Problem with foreach loop

[Rob Coops]

On Mon, Sep 27, 2010 at 9:19 AM, HACKER Nora nora.hac...@stgkk.at wrote:

 Hello list,

 Could someone please explain why this test script:

 my @arr1 = qw(one two three);
 my @arr2 = qw(1 2 3);

 foreach my $arr1 ( @arr1 ) {
print Arr1: $arr1\n;
foreach my $arr2 ( @arr2 ) {
print Arr2: $arr2\n;
if ( $arr2 eq '2' ) {
shift @arr1;
}
}
 }

 produces that result:

 oracle:/opt/data/magna/wartung/work/nora ./test.pl
 Arr1: one
 Arr2: 1
 Arr2: 2
 Arr2: 3
 Arr1: three
 Arr2: 1
 Arr2: 2
 Arr2: 3

 whereas I had expected the output to be like this:

 oracle:/opt/data/magna/wartung/work/nora ./test.pl
 Arr1: one
 Arr2: 1
 Arr2: 2
 Arr2: 3
 Arr1: two   # why not?
 Arr2: 1 # why not?
 Arr2: 2 # why not?
 Arr1: three
 Arr2: 1
 Arr2: 2
 Arr2: 3

 Thanks in advance!

 Regards,
 Nora





Ok, for starters your output is different from the above listed example. The
actual output is:

Arr1: one
Arr2: 1
Arr2: 2
Arr1: two
Arr2: 2
Arr1: three
Arr2: 3

Which makes a lot of sense, you after all start you loop printing Arr1[0]
then in that same loop you print Arr2[0] and Arr2[1] at which point you
shift Arr2; and leave the inner loop, now you are at the end of your main
loop so you print Arr[1] and again start a new inner loop printing Arr[0]
(which thanks to your shift now is equal to 2 and because this is the case
your if statement again shifts Arr2 and ends the inner loop, back in the
main loop there is nothing more to do so we start the loop again this time
printing Arr1[2] and we enter the inner loop printing Arr2[0] which now is
3 so the if statement never becomes true and we exit the inner loop, the
main loop has come to the end of the array as well so we exit that and the
code ends.

There is nothing weird about what is happening here. I think that you are
using a few different scripts to test different things and by now your
output and your actual script do not match which causes most of the
confusion.
I found the best way to actually get your head around the most complex loops
is to write/draw them out and get an actual picture of what is happening. If
you look at most modelling technique this is exactly what they do, it is the
best way for a humans brain to process what is going on. ;-)

Anyway to get the result you want you should simply pop your second array
when you encounter a 3 and in that case of course not print...

foreach my $arr1 ( @arr1 ) {
   print Arr1: $arr1\n;
   foreach my $arr2 ( @arr2 ) {
   if ( $arr2 eq '3' ) {
   pop @arr2;
   } else {
   print Arr2: $arr2\n;
  }
   }
}

That will result in:

Arr1: one
Arr2: 1
Arr2: 2
Arr1: two
Arr2: 1
Arr2: 2
Arr1: three
Arr2: 1
Arr2: 2

Regards,

Rob