Re: hash keys, %

I'm not quite sure what you mean by having a unique URL for each group of twenty. Do you want to generate URLs to pass twenty things at a time to some script?

my @keys  = sort keys %hash;
my $group = 0;

while (my @group = splice(@keys, 0, 20)) {

  ## generate url from stuff in @group
  $group++;

  ## maybe something like this if the items 
  ## are all safe (\w characters):
  my $url = 'script.cgi?' . join '&', map { "x=$_" } @group;

  print qq(<a href="$url">group # $group</a><br>\n);

}
[download]

Even if this isn't quite what you had in mind, maybe the while( .. splice .. ) loop will be a good starting place. The loop condition won't fail until @group gets 0 items, and will still iterate even if @group gets less than 20 the last time through the loop.

Update: if the links only depend on the number of keys, and not the keys themselves, then the number of URLs to print is simply ceil( (keys %hash) / 20 ). ceil simply rounds up, you can import it from the POSIX module.

blokhead

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Re: Re: hash keys, % by sulfericacid (Deacon) on Jul 29, 2003 at 01:02 UTC
I'd like to thank you two for (blokhead and cleverett) for helping with this tricky problem. Of the two methods posted, I went with blockhead's because it looks a lot easier to understand (even though I won't understand fully what's going on until I take a look at splice in a few minutes). The code I used is `my @keys = sort keys %upload; my $group = 0; while (my @group = splice(@keys, 0, 20)) { $group++; my $url = "http://sulfericacid.perlmonk.org/gallery/galleryprint2.pl"; print qq(<a href="$url?page=$group">$group</a><br>\n); }` [download] What exactly is being stored in @keys? The total of keys from the hash or all the key/value information from the hash and using this as an easier method to count each of them? Thanks again for all your help! If you want to see why I needed this, http://sulfericacid.perlmonk.org/gallery/galleryprint2.pl. "Age is nothing more than an inaccurate number bestowed upon us at birth as just another means for others to judge and classify us" sulfericacid	[reply] [d/l]
Re: Re: Re: hash keys, % by blokhead (Monsignor) on Jul 29, 2003 at 01:30 UTC
`splice(@keys, 0, 20)` removes the first 20 items from the array `@keys`, but almost as important, it also returns the items it removed. So it's like using `shift` on a larger chunk. You can use `splice` to simulate `push`, `pop`, `shift`, and `unshift`, as well as insert and remove items from the middle of an array. Of course, the man page for `splice` goes over all this in detail, but it's often useful to think of a splice operation in terms of those 4 basic list operators. But I would suggest not even using this loop, since you never actually seem to use the stuff in `@group` that you splice off. You only seem to be interested in the number to print out, so you could just as easily do this: `use POSIX 'ceil'; my $url = "http://..."; my $num_pages = ceil( (keys %hash) / 20 ); print qq(<a href="$url?page=$_">$_</a><br>\n) for 1 .. $num_pages;` [download] Even if you do use this method, you should still get familiar with `splice`! blokhead	[reply] [d/l] [select]