Re: Newbie queries
dolphin wrote: Hi, Hello, Correct me that the "2" in the following means read? : my ( $label, $value ) = split /,/, $line, 2; The third argument to split determines how many list elements will be returned. For example, if: my $line = 'one,two,three,four,five,six,seven'; Then: split /,/, $line, 2 Would return the list: ( 'one', 'two,three,four,five,six,seven' ) However if you did: my ( $label, $value ) = split /,/, $line; Then split would return the list: ( 'one', 'two', 'three,four,five,six,seven' ) Just as if you had done: my ( $label, $value ) = split /,/, $line, 3; Perl knows how many list elements are expected and only splits enough to satisfy that request. Also, if: my $line = 'one,two,three'; And you do: my @array = split /,/, $line; Then split will return the list: ( 'one', 'two', 'three' ) But if the third argument is a negative number: my @array = split /,/, $line, -1; Then split will return the list: ( 'one', 'two', 'three', '', '', '', '' ) John -- Any intelligent fool can make things bigger and more complex... It takes a touch of genius - and a lot of courage to move in the opposite direction. -- Albert Einstein -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: Newbie queries
From: "dolphin" Hi, Correct me that the "2" in the following means read? : my ( $label, $value ) = split /,/, $line, 2; 2 means that the result of the split() function will be a list with 2 elements. You could also use the split() function without that third parameter that specifies the number of the returned elements: my ( $label, $value ) = split /,/, $line; But the first variant is a little bit faster. Read: perldoc -f split Octavian -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: Newbie queries
On Jan 25, 6:43 pm, orasn...@gmail.com ("Octavian Rasnita") wrote:
> From: "dolphin"
>
>
>
>
>
>
>
>
>
> > Hi,
>
> > I'm learning perl now and would like to find out how to perform the
> > following if given in a text file?
>
> > ,12
> > ,437
> > ,124
> > ,45
> > ,789
> > ,67
> > CCC,567
> > DDD,5
>
> > How to sum up the 2nd column based on the 1st column with the
> > following result:
>
> > :
> > BBB:
> > CCC:
> > DDD:
>
> > Thanks in advance.
>
> You need to read the file line by line:
>
> use strict;
> use warnings;
>
> my %items; #The hash with labels and their corresponding sums
>
> open my $file, '<', 'file_name' or die $!;
>
> while ( my $line = <$file> ) {
>
> # Here split the line:
> my ( $label, $value ) = split /,/, $line, 2;
>
> # Then add each value for its corresponding label:
> $items{$label} += $value;
>
> }
>
> close $file;
>
> # Here print the sorted hash of items:
> for my $label ( sort keys %items ) {
> print "$label: $items{$label}\n";
>
> }
>
> HTH.
>
> Octavian
Hi,
Correct me that the "2" in the following means read?
:
my ( $label, $value ) = split /,/, $line, 2;
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Re: Newbie queries
On Tue, Jan 25, 2011 at 2:43 AM, Octavian Rasnita wrote:
> From: "dolphin"
>>
>> Hi,
>>
>> I'm learning perl now and would like to find out how to perform the
>> following if given in a text file?
>>
>>
>> ,12
>> ,437
>> ,124
>> ,45
>> ,789
>> ,67
>> CCC,567
>> DDD,5
>>
>>
>> How to sum up the 2nd column based on the 1st column with the
>> following result:
>>
>>
>> :
>> BBB:
>> CCC:
>> DDD:
>>
>>
>> Thanks in advance.
>
>
> You need to read the file line by line:
>
>
> use strict;
> use warnings;
>
> my %items; #The hash with labels and their corresponding sums
>
> open my $file, '<', 'file_name' or die $!;
>
> while ( my $line = <$file> ) {
>
> # Here split the line:
> my ( $label, $value ) = split /,/, $line, 2;
>
> # Then add each value for its corresponding label:
> $items{$label} += $value;
> }
>
> close $file;
>
> # Here print the sorted hash of items:
> for my $label ( sort keys %items ) {
> print "$label: $items{$label}\n";
> }
>
> HTH.
>
> Octavian
>
>
> --
> To unsubscribe, e-mail: beginners-unsubscr...@perl.org
> For additional commands, e-mail: beginners-h...@perl.org
> http://learn.perl.org/
>
>
>
Thanks Octavian. I'm also new to Perl and yours was a very simple and
useful explanation.
Cheers,
Mariano
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Re: Newbie queries
From: "dolphin"
Hi,
I'm learning perl now and would like to find out how to perform the
following if given in a text file?
,12
,437
,124
,45
,789
,67
CCC,567
DDD,5
How to sum up the 2nd column based on the 1st column with the
following result:
:
BBB:
CCC:
DDD:
Thanks in advance.
You need to read the file line by line:
use strict;
use warnings;
my %items;#The hash with labels and their corresponding sums
open my $file, '<', 'file_name' or die $!;
while ( my $line = <$file> ) {
# Here split the line:
my ( $label, $value ) = split /,/, $line, 2;
# Then add each value for its corresponding label:
$items{$label} += $value;
}
close $file;
# Here print the sorted hash of items:
for my $label ( sort keys %items ) {
print "$label: $items{$label}\n";
}
HTH.
Octavian
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Newbie queries
Hi, I'm learning perl now and would like to find out how to perform the following if given in a text file? ,12 ,437 ,124 ,45 ,789 ,67 CCC,567 DDD,5 How to sum up the 2nd column based on the 1st column with the following result: : BBB: CCC: DDD: Thanks in advance. -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
