in reply to Re^2: Logical ways to calculate being within two times
in thread Logical ways to calculate being within two times

If I'm understanding you correctly,

Given your 20:00 start time and 12 hours duration, calculate epoch times:

$s = '20:00'; 
$d = 12; 

$e = time; 
$e += 60 until localtime( $e ) =~ m[$s:]; 

$start = $e; 
$end = $start + $d * 3600; 

printf "start:%f end:%f\n",  $start, $end;;
start:1479931244.206990 end:1479974444.206990

[download]

The code above assumes that if a start time is given that is earlier than the current time, it means that time tomorrow.

You might be concerned by the 'crude' mechanism of converting the time to an epoch -- the until loop -- but it will take at most 1/10,000th of a second to do it.

It also assumes that time will be given to the nearest minute; though it is easily changed to allow to the nearest second, but the epoch conversion would then take upto 5/10,000ths of a second.

Of course, you could also load the whole of DateTime to do the conversion, but that probably takes longer just to load than this method :)

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Re^4: Logical ways to calculate being within two times
by stevieb (Canon) on Nov 24, 2016 at 01:28 UTC

    Well, it works just dandy BrowserUK :)

    Needs cleanup and implementation into the various locations the pieces need to be, but it's fast and appears to be accurate after testing with numerous values.

    I'll implement it, then write a boatload of unit tests against the logic. Here's the code I put together with a few comments describing what's what:

    use warnings;
use strict;
use feature 'say';

# simulate the light and times db entries

my $light = 0;
my $on = '18:00';
my $hrs = 12;

my $now = time;
my ($start, $end);

# the following will be run once only when
# the main webapp is started. This sets the
# initial lights-on/off times into the db.
# of course, it'll just overwrite without first
# checking if the time was set previously or not

if (! $start){
    set_times();
    $start = $start - 24 * 3600;
    $end = $end - 24 * 3600;
}

# simulate event calling the light method

action_light();

say "light is on" if $light;

# object method that the event calls

sub action_light {
    if ($now > $start && $now < $end){
        if (! $light){
            $light = 1;
        }
    }
    elsif ($light) {
        $light = 0;
        set_times();
    }
}

# obj method called by action_light() and upon
# main webapp startup

sub set_times {
    my $time = time;
    $time += 60 until localtime($time) =~ /$on:/;
    $start = $time;
    $end = $start + $hrs * 3600;
}

    [download]

    Thanks for your input!

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