joec_ has asked for the wisdom of the Perl Monks concerning the following question:

Hi, i have a hash of names and random numbers. What i would like to do is end up with a full print of the list and other lists (more hashes maybe?) like this:

Full list:
-------
Greg, 1111
Caroline,2222
Joe,3333
...
Edited lists:
-----------
Caroline, 2222
Joe, 3333
....
* Note removal of first element

-----------
Greg, 1111
Joe, 3333
....
* Note removal of second element

The code i have so far is:

#!/usr/bin/perl

use strict;
use warnings;

my $range=8999;
my $min = 1000;
my @names = qw(Greg Caroline Joe Dom Mary Gerard Mark Clare Adam Damia
+n Debbie Conor Cassie John Jane Mike);
my %hash;

foreach my $n (@names){
    my $r = int(rand($range))+$min;
    $hash{$n}=$r;
}

[download]

I would also like the lists to match the order of the @names array
The logic is eluding me but i can guess that its really simple.

Any suggestions appreciated.

Thanks
Joe

Replies are listed 'Best First'.
Re: Print hash except first value
by ww (Archbishop) on Dec 21, 2008 at 02:31 UTC
    Re your use of a hash and your desire to omit the "first" element: You should understand that the order of a hash's elements is not defined; that is, the order in which you create the elements will be the order in which the elements are processed only by chance, absent use of sort or a Tie::... modules.
[reply]
[d/l]
[select]
      While the order of hash elements is not defined, for a given hash, the keys will be returned in a consistent order as long as the hash is not altered. The OP's desire to generate the n possible lists of n - 1 elements (key/value pairs) from a list of n elements is consistent with the use of a hash.
[reply]
Re: Print hash except first value
by ikegami (Patriarch) on Dec 20, 2008 at 22:20 UTC

    Some alternatives: 

    my $first = 1;
for my $n (sort { $hash{$a} <=> $hash{$b} } keys %hash){
   if ($first) {
      $first = 0;
      next;
   }

   ...
}

    [download]
    my @names_by_val = sort { $hash{$a} <=> $hash{$b} } keys %hash;
shift(@names_by_val);
for my $n (@names_by_val) {
   ...
}

    [download]
    my @names_by_val = sort { $hash{$a} <=> $hash{$b} } keys %hash;
for my $n (@names_by_val[1..$#names]) {
   ...
}

    [download]

    A hash isn't needed at all. 

    my %hash;
foreach my $n (@names){
    my $r = int(rand($range))+$min;
    $hash{$n}=$r;
}
my @names_by_val = sort { $hash{$a} <=> $hash{$b} } keys %hash;

    [download]

    can be replaced with 

    use List::Util qw( shuffle );
my @shuffled_names = shuffle @names;

    [download]

    Update: Doesn't answer the question.

[reply]
[d/l]
[select]

      Here's a way using two arrays. You can iterate over the index of the elements in each array while preserving the order of the @names. 

      my @names = qw(Greg Caroline Joe Dom Mary Gerard Mark Clare Adam Damia
+n Conor Cassie John Jane Mike);
my $max_rand = 8999;
my $min_rand = 0;
my @random_array = map{ int(rand($max_rand + 1)) + $min_rand } @names;

foreach my $index (0..$#names) {
    print "$names[$index], $random_array[$index]\n";
}

      [download]

      In addition, you could easily not print a line based on its index number. For example inside the print loop add: 

      my $skip_index = 0;
next if $index == $skip_index;

      [download]
[reply]
[d/l]
[select]
      thanks for the quick reply, what does each section of your code do?
[reply]
        They iterate over the (keys of the) hash, skipping the first one

        Update: ...which I now see isn't what you asked. In fact, I don't know what you are trying to do. I don't see what the hash has to do with anything. As best as I can tell, you want a variation of 

        for my $skip (0..$#names) { 
   print("-------\n");
   for my $i (0..$#names) {
      next if $i == $skip;
      my $n = $names[$i];
      print("$n, $hash{$n}\n");
   }
   print("* Note removal of element $skip\n");
   print("\n");
}

        [download]
[reply]
[d/l]

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