Need explanation about this code.
Hello,
I have problems in understanding $...@$ use ?
1- my $ref = $$temp_sth - fetchall_arrayref({});
for(my $i=0; $i = $...@$ref}; $i++) {
push(@$temp_table,$ref-[$i]);}
Can some one explain the under given function.
2- sub buildSensorsHashtable
{
my ($dbh) = @_;
my $error = 0;
my $query = SELECT * FROM Sensors;
my $sth = $dbh-prepare($query);
if(!$sth || !($sth-execute())) { $error = 1 ;
}
my $ref = $sth-fetchall_arrayref({});
my %s;
my @s = @$ref;
foreach (@s)
{
if($_-{StatusID} eq 1) { $s{$_-{IP}} = $_-{SensorID}; }
}
return (\%s,$error);
3- Which is the best tool for debuging perl programs having CGI support. I
used DDD but that does not support CGI.
Regards,
Raheel
Re: Need explanation about this code.
On 10/8/09 Thu Oct 8, 2009 9:00 AM, Raheel Hassan
raheel.has...@gmail.com scribbled:
Hello,
I have problems in understanding $...@$ use ?
1- my $ref = $$temp_sth - fetchall_arrayref({});
for(my $i=0; $i = $...@$ref}; $i++) {
For any array @a, the largest index is given by $#a.
$ref is a reference to an array, as returned by the fetchall_arrayref
method.
@{$ref} is the array returned.
Therefore, $...@$ref} is the largest index of the returned array, i.e., the
index of the last element of the array.
push(@$temp_table,$ref-[$i]);}
Can some one explain the under given function.
It looks like a function that queries a database, getting all of the data
from a table called Sensors. Then for each row in that table, checks the
value of the column labeled StatusID, and, if the value of that column is
1, adds an entry to a hash with the contents of the IP column as key,
and the value taken from the column SensorID. The function returns a list,
consisting of a reference to the hash and the value of the $error variable,
which will be 0 if no error occurred, and 1 if an error did occur.
2- sub buildSensorsHashtable
{
my ($dbh) = @_;
my $error = 0;
my $query = SELECT * FROM Sensors;
my $sth = $dbh-prepare($query);
if(!$sth || !($sth-execute())) { $error = 1 ;
}
my $ref = $sth-fetchall_arrayref({});
my %s;
my @s = @$ref;
foreach (@s)
{
if($_-{StatusID} eq 1) { $s{$_-{IP}} = $_-{SensorID}; }
}
return (\%s,$error);
3- Which is the best tool for debuging perl programs having CGI support. I
used DDD but that does not support CGI.
Debugging CGI programs can be difficult. You need access to the HTTP logs.
You can help yourself by following the advice given in the FAQ How can I
get better error messages from a CGI program? (see 'perldoc -g CGI'). Try
to set up a test environment, either by executing the CGI program from the
command line (by supplying the various parameters needed) or by running the
program first on a local server where you have access to the logs.
Good luck.
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Re: Need explanation about this code.
Raheel Hassan wrote:
Hello,
Hello,
I have problems in understanding $...@$ use ?
1- my $ref = $$temp_sth - fetchall_arrayref({});
for(my $i=0; $i = $...@$ref}; $i++) {
push(@$temp_table,$ref-[$i]);}
$...@$ref} should be $#{$ref} or simply $#$ref
And
for(my $i=0; $i = $...@$ref}; $i++) {
should be
for my $i ( 0 .. $#$ref ) {
And
for(my $i=0; $i = $...@$ref}; $i++) {
push(@$temp_table,$ref-[$i]);}
should be
push @$temp_table, @$ref;
John
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for output from other unix commands
I'm just looking for a push to get started... I do have some perl skills (pretty lowlevel to be sure) so can do basic formating with printf and such. But here... I expect my input to be pretty uniform actually already formatted ok. Except, 1 or 2 lines somewhere in the input that will be longer and make reading the output a bit of a chore. I want to catch those long lines and format them like one might format a news/mail message... wrapped at column 72 or so but also indented whatever spcs looks good. I looked at perldoc -f format but that says its about pictures and doesn't appear to be intended to format text. Imagine input like: somevar=settingotherinfootherinfo2 somevar=setting, that , is way longer than any thing else in the history of mankindotherinfootherinfo2 somevar=settingotherinfootherinfo2 ---- ---=--- - The `var=setting' with all the baloney should be wrapped but still end up with the last 2 elements lined up like the other lines: somevar=settingotherinfootherinfo2 somevar=setting, that , is way longer than any thing else in the history of mankind otherinfootherinfo2 somevar=settingotherinfootherinfo2 -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: adding populations
Jesus Fernandez wrote:
Dear friends,
Hello
I'm trying to write a program that draws 5,000 numbers from an exponential
distribution with mean 4N/k(k-1)
N=10 000
k = 25
I have this:
#!jesusafernandez/bin/perl
use warnings;
use strict;
$k = 25;
my $k = 25;
$N = 1;
my $N = 10_000;
for ($samp=0; $samp5000; $samp++)
{
for my $samp ( 0 .. 4_999 ) {
while ($k!= $25)
The numeric variable $25 can only be used with regular expressions.
Perhaps you meant:
while ( $k != 25 )
{
$mean = 4$N/$k($k-1));
You are missing an operator between 4 and $N and between $k and ($k-1).
Perhaps you meant:
my $mean = 4 * $N / $k * ( $k - 1 );
$time = (-log (rand)*$ mean);
Although a space between '$' and 'mean' is allowed it is usually not
good practice.
my $time = -log( rand ) * $mean;
push (@xx,$time);
$k=$k-y}
The string literal 'y' should be in quotes, but a string literal used in
numerical context will just evaluate to the number 0 so:
$k -= 0;
}
Although using 0 there does not make much sense.
print $time\n;
You are missing the closing } for the for loop.
John
--
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destructive forces in the universe: entropy and
human stupidity. -- Damian Conway
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Re: for output from other unix commands
Hi Harry! On Thursday 08 Oct 2009 21:29:04 Harry Putnam wrote: I'm just looking for a push to get started... I do have some perl skills (pretty lowlevel to be sure) so can do basic formating with printf and such. But here... I expect my input to be pretty uniform actually already formatted ok. Except, 1 or 2 lines somewhere in the input that will be longer and make reading the output a bit of a chore. I want to catch those long lines and format them like one might format a news/mail message... wrapped at column 72 or so but also indented whatever spcs looks good. I looked at perldoc -f format but that says its about pictures and doesn't appear to be intended to format text. Have you tried http://search.cpan.org/dist/Perl6-Form/ ? Or maybe: http://search.cpan.org/dist/Text-Tabs+Wrap/ Regards, Shlomi Fish -- - Shlomi Fish http://www.shlomifish.org/ http://www.shlomifish.org/humour/ways_to_do_it.html Chuck Norris read the entire English Wikipedia in 24 hours. Twice. -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: for output from other unix commands
Shlomi Fish shlo...@iglu.org.il writes: Hi Harry! [...] I want to catch those long lines and format them like one might format a news/mail message... wrapped at column 72 or so but also indented whatever spcs looks good. I looked at perldoc -f format but that says its about pictures and doesn't appear to be intended to format text. Have you tried http://search.cpan.org/dist/Perl6-Form/ ? Or maybe: http://search.cpan.org/dist/Text-Tabs+Wrap/ Those do look tempting, especially the first, but both seem a little heavy handed for what I need... And might take me a good bit to figure out how to use themI may just look for a specific line and torture it till it looks like I want it too. At this point my input will only include one recalcitrant line where there is a problem... but it makes the tool whos' output I want to fix put out all lines to match that long one... Where all but one line follow this: some setting=wordsetting=word setting=word ---- ---=--- - Adding the bad line does this: some setting=word lots of extra space now here setting=word setting=word some OtherSetting=a whole big long line of never ending words like this one causing the program to ouput setting=word setting=word ---- ---=--- - So the line with OtherSetting is causing all lines to be output with space to accommodate the long setting. The tool provided by OS does that on its own so I want to fix its ouput... I guess just watching for that line.. and manually folding it with perl will do what I want. If I can figure out how to clip out the extra space now included in all other lines. -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Re: for output from other unix commands
On 10/8/09 Thu Oct 8, 2009 3:56 PM, Harry Putnam rea...@newsguy.com scribbled: Shlomi Fish shlo...@iglu.org.il writes: Hi Harry! [...] I want to catch those long lines and format them like one might format a news/mail message... wrapped at column 72 or so but also indented whatever spcs looks good. I looked at perldoc -f format but that says its about pictures and doesn't appear to be intended to format text. Have you tried http://search.cpan.org/dist/Perl6-Form/ ? Or maybe: http://search.cpan.org/dist/Text-Tabs+Wrap/ Those do look tempting, especially the first, but both seem a little heavy handed for what I need... And might take me a good bit to figure out how to use themI may just look for a specific line and torture it till it looks like I want it too. At this point my input will only include one recalcitrant line where there is a problem... but it makes the tool whos' output I want to fix put out all lines to match that long one... Where all but one line follow this: some setting=wordsetting=word setting=word ---- ---=--- - Adding the bad line does this: some setting=word lots of extra space now here setting=word setting=word some OtherSetting=a whole big long line of never ending words like this one causing the program to ouput setting=word setting=word ---- ---=--- - So the line with OtherSetting is causing all lines to be output with space to accommodate the long setting. The tool provided by OS does that on its own so I want to fix its ouput... I guess just watching for that line.. and manually folding it with perl will do what I want. If I can figure out how to clip out the extra space now included in all other lines. You might try splitting the line on whitespace, extracting the first two and last two elements, then joining the remainder back with a space. You can then test the length of the middle string for excessive length and print or trim accordingly. This will concatenate any extra spaces in the middle string. This only works if the first two and last two fields contain no spaces. -- To unsubscribe, e-mail: beginners-unsubscr...@perl.org For additional commands, e-mail: beginners-h...@perl.org http://learn.perl.org/
Building a record on the fly via hash of hashes
Hello All,
I am doing some file reading operation, and parsing the data(its a CSV file)
with a hash reference and then intend to store it in a record.
something like:
loop: until file ends;
$hashref-{'A'}=$filehandle-{'Action'};
$hashref-{'B'}= $filehandle-{'Name'};
$hashref-{'C'}= $filehandle-{'System'};
$hashref-{'D'}=($filehandle-{'Price'});
$recordref-{$hashref-{'B'}}= $hashref;
loop : ends
Here Action, Name,System,price are the CSV headers.
Now, when the first line is read, the details are parsed and stored in the
$recordref as a hash reference. Now when the loop iterates, and goes to the
second line. The first line contents are lost. Because the hash reference now
points to the newer data.
How do I overcome this?
More importantly do we have a push equivalent for hash of hashes?
Soham
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Re: Building a record on the fly via hash of hashes
At 10:14 PM -0700 10/8/09, Soham Das wrote:
Hello All, I am doing some file reading operation, and parsing the
data(its a CSV file) with a hash reference and then intend to store
it in a record. something like: loop: until file ends;
$hashref-{'A'}=$filehandle-{'Action'};
$hashref-{'B'}= $filehandle-{'Name'};
$hashref-{'C'}= $filehandle-{'System'};
$hashref-{'D'}=($filehandle-{'Price'});
$recordref-{$hashref-{'B'}}= $hashref; loop : ends
You are better off including some actual Perl code, including some sample data.
Here Action, Name,System,price are the CSV headers. Now, when the
first line is read, the details are parsed and stored in the
$recordref as a hash reference. Now when the loop iterates, and goes
to the second line. The first line contents are lost. Because the
hash reference now points to the newer data. How do I overcome this?
More importantly do we have a push equivalent for hash of hashes?
No. Unless each record has a unique key, you are better off using an
array of hashes, rather than a hash of hashes. Of course, you could
use the line number as a unique key, but an array would be more
efficient.
--
Jim Gibson
j...@gibson.org
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Re: Building a record on the fly via hash of hashes
The code:
From: Jim Gibson jimsgib...@gmail.com
To: beginners@perl.org
Sent: Fri, 9 October, 2009 11:00:55 AM
Subject: Re: Building a record on the fly via hash of hashes
At 10:14 PM -0700 10/8/09, Soham Das wrote:
Hello All, I am doing some file reading operation, and parsing the data(its a
CSV file) with a hash reference and then intend to store it in a record.
something like: loop: until file ends;
$hashref-{'A'}=$filehandle-{'Action'}; $hashref-{'B'}=
$filehandle-{'Name'}; $hashref-{'C'}= $filehandle-{'System'};
$hashref-{'D'}=($filehandle-{'Price'}); $recordref-{$hashref-{'B'}}=
$hashref; loop : ends
You are better off including some actual Perl code, including some sample data.
Here Action, Name,System,price are the CSV headers. Now, when the first line
is read, the details are parsed and stored in the $recordref as a hash
reference. Now when the loop iterates, and goes to the second line. The first
line contents are lost. Because the hash reference now points to the newer
data. How do I overcome this? More importantly do we have a push equivalent
for hash of hashes?
No. Unless each record has a unique key, you are better off using an array of
hashes, rather than a hash of hashes. Of course, you could use the line number
as a unique key, but an array would be more efficient.
-- Jim Gibson
j...@gibson.org
-- To unsubscribe, e-mail: beginners-unsubscr...@perl.org
For additional commands, e-mail: beginners-h...@perl.org
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Re: Building a record on the fly via hash of hashes
The Code:
use strict;
use warnings;
use Tie::Handle::CSV;
my $qbook = Tie::Handle::CSV-new('C:\Documents and Settings\Soham
Das\Desktop\Quotes.csv',header=1);
my $tradebook = Tie::Handle::CSV-new('C:\Documents and Settings\Soham
Das\Desktop\Transactions.csv',header=1);
my $dailytrade={};
my $portfolio={};
my $singletrade={};
while(my $mktdates =$qbook)
{
while(my $trades=$tradebook)
{
if($trades-{'Date'} eq $mktdates-{'Date'})
{
$singletrade-{'Action'}=$trades-{'Action'};
$singletrade-{'Scrip'}= $trades-{'Scrip'};
$singletrade-{'Shares'}= $trades-{'Shares'};
$singletrade-{'Price'}=($trades-{'Price'})*1.00845;
$dailytrade-{$singletrade-{'Scrip'}}= $singletrade;
# print $dailytrade-{$singletrade-{'Scrip'}}-{'Price'},\n;
}
#Update the portfolio
}
}
close $qbook ;
close $tradebook;
Soham
P.S: apologies for the previous mail being a blank mail, it was a mistake
From: Soham Das soham...@yahoo.co.in
To: beginners@perl.org
Sent: Fri, 9 October, 2009 11:02:51 AM
Subject: Re: Building a record on the fly via hash of hashes
The code:
From: Jim Gibson jimsgib...@gmail.com
To: beginners@perl.org
Sent: Fri, 9 October, 2009 11:00:55 AM
Subject: Re: Building a record on the fly via hash of hashes
At 10:14 PM -0700 10/8/09, Soham Das wrote:
Hello All, I am doing some file reading operation, and parsing the data(its a
CSV file) with a hash reference and then intend to store it in a record.
something like: loop: until file ends;
$hashref-{'A'}=$filehandle-{'Action'}; $hashref-{'B'}=
$filehandle-{'Name'}; $hashref-{'C'}= $filehandle-{'System'};
$hashref-{'D'}=($filehandle-{'Price'}); $recordref-{$hashref-{'B'}}=
$hashref; loop : ends
You are better off including some actual Perl code, including some sample data.
Here Action, Name,System,price are the CSV headers. Now, when the first line
is read, the details are parsed and stored in the $recordref as a hash
reference. Now when the loop iterates, and goes to the second line. The first
line contents are lost. Because the hash reference now points to the newer
data. How do I overcome this? More importantly do we have a push equivalent
for hash of hashes?
No. Unless each record has a unique key, you are better off using an array of
hashes, rather than a hash of hashes. Of course, you could use the line number
as a unique key, but an array would be more efficient.
-- Jim Gibson
j...@gibson.org
-- To unsubscribe, e-mail: beginners-unsubscr...@perl.org
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