mt2k has asked for the wisdom of the Perl Monks concerning the following question:

I have a really hard question that I can't seem to figure out (okay, so I *can't* figure it out!)...

How would I go about sorting times, that include the hour, minutes, and AM/PM, into a well-sorted list??

Here is what the times I need to sort would look like:

3:15PM
1:00AM
8:30AM
6:15PM
2:45PM

[download]

The way I want these sorted is in the order that the times pass during a day. So, the above examples should sort out to:
1:00AM
8:30AM
2:45PM
3:15PM
6:15PM

[download]

So basically, how would I go sorting these? I can't use a simple sort { $a cmp $b}, because then it sorts to: 

1:00AM
2:45PM
3:15AM
6:15AM
8:30AM

[download]

Thanks in advance!

Replies are listed 'Best First'.
Re: Sorting Times
by clintp (Curate) on Apr 28, 2001 at 05:21 UTC
    This is a good place for a Schwartzian transform... 
    @r=qw( 1:00AM
  2:45PM
  8:30AM
  3:15PM
  6:15PM );

 @t=map { $_->[0] }
  sort { $a->[1] <=> $b->[1] }
  map { $a=$_;
        s/://;
        s/(\d+)(\w)M/$1+($2 eq "P"?1200:0)/e;
       [ $a, $_ ] } @r;

# @t has your sorted times.

    [download]
    The second map can be shortened up a bit. I'm just making what's going on there a little more obvious...
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[d/l]
Re: Sorting Times
by boo_radley (Parson) on Apr 28, 2001 at 05:02 UTC
    well, uh, how about military time?
    there's lots of good ways to do this. date::manip and all that. how about something less optimal, but wacky?
     
$_= "11:12AM";
tr/://d;
if (s/(\d\d)(\d\d?)([A|P])M/$1$2/) {
    if ($3 eq "P") {$_ +=1200 unless $1==12};
}
print $_;

    [download]
    update Military Time ™ crazyinsomniac.
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[d/l]
Re: Sorting Times
by Rhandom (Curate) on Apr 28, 2001 at 06:30 UTC
    You could also ... 
    %h = map {
 $a=$_;
 s{(\d+):(\d+)(A|P)}
  { sprintf("%02d:%02d",$1+($3 eq 'A'?0:12),$2) }e;
 $_ => $a
} @times;

    [download]
    Now you have a hash where the key is military time and the value is your original time. You can do whatever want after that (including foreach (sort keys %h)).

    my @a=qw(random brilliant braindead); print $a[rand(@a)];
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[d/l]
(tye)Re: Sorting Times
by tye (Sage) on Apr 28, 2001 at 10:17 UTC

    I agree with the oft-repeated idea of converting to a padded 24-hour notation (or "military time" where the ":" is dropped), but everyone got it wrong. Yes, you need to add 12 to the "hours" for PM times, but you also need to subtrace 12 hours for 12AM times. q-:

            - tye (but my friends call me "Tye")
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Re: Sorting Times
by Trimbach (Curate) on Apr 28, 2001 at 07:49 UTC
    Depending on your situation it might be a good idea to rethink your data. Personally, I'm a big fan of doing date/time calculations using # of seconds since the epoch (that is, on Unix, time and date are described as the number of seconds since January 1, 1970.) Number of seconds is a very handy format: it's easy to sort, easy to manipulate (need to add or subtract a minute/hour/day/month? Piece of cake!) and easily transferable back and forth into something legible using localtime() and Time::Local.

    Of course, you might not have that option... but IMHO dealing in epoch-time is a good habit to get into.

    Gary Blackburn
    Trained Killer

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      it's easy to sort

      Beware the ides of September.
      <code> perl -e 'print time."\n".localtime(1_000_000_000)."\n";'

      my @a=qw(random brilliant braindead); print $a[rand(@a)];
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        Says Rhandom:
        Beware the ides of September.
        perl -e 'print time."\n".localtime(1_000_000_000)."\n";'
        Nice thought, but the ides of September don't begin until 1_000_339_200. (Plus or minus a bit, depending on time zones and local conventions.)

        --
        Mark Dominus
        Perl Paraphernalia

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Re: Sorting Times
by japhy (Canon) on Apr 29, 2001 at 01:09 UTC
    I'd forego the ST, and use a GRT instead: 
    @s =
  map { (my $x = join '', reverse /(..)\s*(.*)/) =~ s/00:/12:/; $x }
  sort
  map { (my $x = sprintf "%2s%5s", reverse /(.{4,5})(..)/) =~ s/12:/00
+:/; $x }
  @t;

    [download]


    japhy -- Perl and Regex Hacker
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[d/l]
Re: Sorting Times
by mt2k (Hermit) on Apr 28, 2001 at 23:26 UTC
    I used clintp's version. Works perfectly! Thanks to everyone for the help.
[reply]

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