http://qs321.pair.com?node_id=1212370


in reply to Re^2: Sorting hash
in thread Sorting hash

Hi,

there you go.

i must confess that i missed also 1 thing in your sort function.

the cpu percentage will not interpreted as an numeric value, so you have to use cmp instead of <=>.

see perlop

#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

my %results = (
    'hostname1' => {
        '1' => {
            'pass' => 1,
            'cpu' => '0.07%',
            'box_name' => 'hostname',
            'capacity' => '0.41%'
        }
    },
    'hostname2' => {
        '1' => {
            'pass' => 1,
            'cpu' => '0.04%',
            'box_name' => 'hostname',
            'capacity' => '0.25%'
        }
    }
);

my $results = \%results;
                                                
foreach my $router ( sort { $results->{$a}{1}{cpu} cmp $results->{$b}{
+1}{cpu} } keys %{results} ) {
    print Dumper($results->{$router});
}

[download]

Replies are listed 'Best First'.
Re^4: Sorting hash
by pryrt (Abbot) on Apr 05, 2018 at 19:30 UTC
    the cpu percentage will not interpreted as an numeric value

    Actually, due to Perl trying to numberify a string in numeric context, it turns out percents written as strings get reasonably interpreted as numbers: 

    C:\WINDOWS\system32>perl -MDevel::Peek=Dump -le " $a = qq(3.14%); Dump
+ $a; $b = qq(2.718%); Dump $b; print $a <=> $b; Dump $a; Dump $b"
SV = PV(0x1daf58) at 0x44d2660
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x44ebf28 "3.14%"\0
  CUR = 5
  LEN = 10
  COW_REFCNT = 1
SV = PV(0x1dafb8) at 0x44d2300
  REFCNT = 1
  FLAGS = (POK,IsCOW,pPOK)
  PV = 0x44ebe68 "2.718%"\0
  CUR = 6
  LEN = 10
  COW_REFCNT = 1
1
SV = PVNV(0x1d9288) at 0x44d2660
  REFCNT = 1
  FLAGS = (POK,IsCOW,pNOK,pPOK)
  IV = 0
  NV = 3.14
  PV = 0x44ebf28 "3.14%"\0
  CUR = 5
  LEN = 10
  COW_REFCNT = 1
SV = PVNV(0x1d9268) at 0x44d2300
  REFCNT = 1
  FLAGS = (POK,IsCOW,pIOK,pNOK,pPOK)
  IV = 2
  NV = 2.718
  PV = 0x44ebe68 "2.718%"\0
  CUR = 6
  LEN = 10
  COW_REFCNT = 1

    [download]
    ... They start out as just the string (PV); but after running numeric compare, you can see that it had the right output value for $a <=> $b (1) and afterward, they also have the reasonable floating-point value (NV) of 3.14 and 2.718.

[reply]
[d/l]
[select]
      Hi,

      you are right, but you get an warning:

      Argument "0.04%" isn't numeric in numeric comparison (<=>)

      the sorting order, in this trivial example, is the same, but who knows what shows up in the real world.

      so a numeric compare seems to be the more obvious choice in this case.

      of course there are several ways to get rid of the warnings and using numeric comparison.

[reply]
[d/l]
        You're right. That'll remind me to turn on warnings even for oneliners...
[reply]

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