Breaking a list down
This is beyond me.
I have a list like this:
200611
200612
200701
200702
Etc.
I need to pull out the year (i.e., 2006) and only print it only once. The other 2 digits represent the months and all these need to be shown. So I can have something along these lines:
2006
11
12
2007
01
02
Is there a simple way to do that in Perl please?
thanks - Ted
Abhishek Reddy posted this at 22:38 — 22nd April 2007.
He has: 3,348 posts
Joined: Jul 2001
Here's a quick attempt at it. The function [incode]group_lines_by_year[/incode] takes an array of lines as you showed and returns an array of reorganised lines that you can print any way you like.
sub group_lines_by_year {
@ret = (); $current_group = null;
foreach (@_) {
/([0-9]{4})([0-9]{2})/;
($year, $month) = ($1, $2);
if ($year != $current_group) {
$current_group = $year;
push (@ret, $year);
}
push (@ret, $month);
}
return @ret;
}
@lines = ('200611','200612','200701','200702');
print join("\n", group_lines_by_year(@lines)) . "\n";
It works simply by walking through every line and checking if the date is in the "current group". If it isn't, then it updates the current group. Each year and month is collected in an array and returned.
Tedh posted this at 07:20 — 23rd April 2007.
They have: 21 posts
Joined: Nov 2004
Thanks Abhishek, that works great. I did a text file with several yearsmonths, read into @lines array and got a nice list.
Is there a way I can add links to each element? Your code is bit tight. I did manage line breaks like so:
print join("<br>\n", group_lines_by_year(@lines)) . "\n";But couldn't get any further.
The end result will reside in a list that a user can click the year or the month and an action will take place. The year link will cause the months to drop down (JS and/or CSS) and the month links will open a file.
I'm more a designer than programmer, but manage to get some Perl working.
Thanks again - Ted
kb posted this at 07:49 — 23rd April 2007.
He has: 1,380 posts
Joined: Feb 2002
(not related, but you should try PHP
things would be much simpler if you didn't have to code in Perl...just a thought)
Abhishek Reddy posted this at 21:46 — 23rd April 2007.
He has: 3,348 posts
Joined: Jul 2001
You don't have to print it as I gave in my example. You could do something like this:
foreach (group_lines_by_year(@lines)) {print "<a href=\"foo\">" . $_ . "</a><br />\n";
}
The point is, the function [incode]group_lines_by_year[/incode] returns a list, with which you can do anything you want.
I disagree. The algorithm would be identical. Its expression in PHP -- aside from Perl's shorthand regex and special variables -- would also be nearly identifcal. The difference is negligible.
timjpriebe posted this at 22:21 — 23rd April 2007.
He has: 2,667 posts
Joined: Dec 2004
As someone who programs in both Perl and PHP on a regular basis, I would have to disagree with Abhishek and agree with brady.k. I've found that for non-programmers or new programmers, PHP is much easier and simpler to pick up.
And if I had my choice, I would be programming exclusively in PHP with no Perl at all.
Tim
http://www.tandswebdesign.com
Abhishek Reddy posted this at 09:23 — 24th April 2007.
He has: 3,348 posts
Joined: Jul 2001
The only reason I can think of for why this can be is that documentation and support for PHP is easier to find -- including tutorials, articles and forums. However, owning the right book or searching and asking in the right places is enough to overcome that handicap for Perl.
There is very little intrinsic in either of the languages and systems that makes one easier than the other, for a newcomer. Equally, there are parts that may be harder in one or the other. I'm not even sure libraries (standard or otherwise) really count for or against either choice, as they're roughly of the same breadth and quality.
For the record, here's the function in question written in PHP:
<?phpfunction group_lines_by_year ($lines) {
$ret = array(); $current_group = NULL;
foreach ($lines as $line) {
preg_match(\"/([0-9]{4})([0-9]{2})/\", $line, $matches);
$year = $matches[1]; $month = $matches[2];
if ($year != $current_group) {
$current_group = $year;
array_push($ret, $year);
}
array_push($ret, $month);
}
return $ret;
}
?>
It is, for all intents and purposes, exactly the same as the Perl code. I might contend that the Perl version is less verbose and more readable too, but that's a matter of taste and style.
So it's not clear that PHP is in any way advantageous here. There's no compelling reason to make such an arbitrary switch.
Tedh posted this at 10:49 — 24th April 2007.
They have: 21 posts
Joined: Nov 2004
Ok,
This is where I've got to at the moment:
@lines = ('200611','200612','200701','200702');
sub parse_date_line {
/([0-9]{4})([0-9]{2})/;
return ($1, $2);
}
sub group_lines_by_year {
@ret = (); $current_group = null;
foreach (@_) {
($year, $month) = parse_date_line $_;
if ($year != $current_group) {
$current_group = $year;
push (@ret, "<a href\=\"\#nogo\">$year<\/a>");
}
push (@ret, "<a href\=\"\#thearchivecodegoeshere\">$month<\/a>");
}
return @ret;
}
foreach (group_lines_by_year(@lines)) {
print $_ . "<br>\n";
}
I still have to see if I can integrate this with the rest of my code. Eventually this will be part of a small blog system (DaBloggo) which people will be able to download free from my site. Abhishek, you'll get listed in the credits for this (unless you don't want to be).
It's all in Beta Version at the moment - so's I can get input from others and stuff right.
cheers - Ted
kb posted this at 23:17 — 23rd April 2007.
He has: 1,380 posts
Joined: Feb 2002
Sorry, I didn't mean to get everyone off topic. I just wanted to poke at Perl a little. I mentioned it because I think PHP is easier to read than Perl, and if that's the only real benefit, it's all the more reason to use it.
Tedh posted this at 07:40 — 24th April 2007.
They have: 21 posts
Joined: Nov 2004
I should have thought of that Abhishek. Thanks. I'll have to try and split that down so the year can have it's blank link and the months their code.
As for the PHP. Learning a bit of Perl does my head in at times, to begin a whole new language . . . . aaargh!
- Ted
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