Nautical bell

Nautical bell is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

The task is to write a small program that emulates a nautical bell producing a ringing bell pattern at certain times throughout the day. The bell timing should be in accordance with Greenwich Mean Time, unless locale dictates otherwise.

It is permissible for the program to daemonize, or to slave off a scheduler, and it is permissible to use alternative notification methods (such as producing a written notice "Two Bells Gone"), if these are more usual for the system type.

D

This code uses local time instead of Greenwich Mean Time. <lang d>import std.stdio, core.thread, std.datetime;

class NauticalBell : Thread {

   private shared bool stopped;

   this() {
       super(&run);
   }

   void run() {
       uint numBells;
       auto time = cast(TimeOfDay)Clock.currTime();
       auto next = TimeOfDay();

       void setNextBellTime() {
           next += minutes(30);
           numBells = 1 + (numBells % 8);
       }

       while (next < time)
           setNextBellTime();

       while (!this.stopped) {
           time = cast(TimeOfDay)Clock.currTime();
           if (next.minute == time.minute &&
                   next.hour == time.hour) {
               immutable bells = numBells == 1 ? "bell" : "bells";
               writefln("%s : %d %s", time, numBells, bells);
               setNextBellTime();
           }
           sleep(dur!"msecs"(100));
           yield();
        }
    }

    void stop() {
       this.stopped = true;
    }

}

void main() {

   auto bells = new NauticalBell();
   bells.isDaemon(true);
   bells.start();
   try {
       bells.join();
   } catch (ThreadException e) {
       writeln(e.msg);
   }

}</lang>

Output:

09:30:00 : 3 bells
10:00:00 : 4 bells
10:30:00 : 5 bells
11:00:00 : 6 bells
11:30:00 : 7 bells
12:00:00 : 8 bells
12:30:00 : 1 bell
13:00:00 : 2 bells
13:30:00 : 3 bells
14:00:00 : 4 bells
14:30:00 : 5 bells
15:00:00 : 6 bells
15:30:00 : 7 bells
16:00:00 : 8 bells
16:30:00 : 1 bell
17:00:00 : 2 bells
17:30:00 : 3 bells
18:00:00 : 4 bells
18:30:00 : 5 bells
19:00:00 : 6 bells
19:30:00 : 7 bells
20:00:00 : 8 bells
20:30:00 : 1 bell
21:00:00 : 2 bells
21:30:00 : 3 bells
22:00:00 : 4 bells
22:30:00 : 5 bells
23:00:00 : 6 bells
23:30:00 : 7 bells
00:00:00 : 8 bells
00:30:00 : 1 bell
01:00:00 : 2 bells
01:30:00 : 3 bells
02:00:00 : 4 bells
02:30:00 : 5 bells
03:00:00 : 6 bells
03:30:00 : 7 bells
04:00:00 : 8 bells
04:30:00 : 1 bell
05:00:00 : 2 bells
05:30:00 : 3 bells
06:00:00 : 4 bells
06:30:00 : 5 bells
07:00:00 : 6 bells
07:30:00 : 7 bells
08:00:00 : 8 bells
08:30:00 : 1 bell
09:00:00 : 2 bells

REXX

The local time is used instead of Greenwich mean time.

If any arguments are specified, that text is used as a prefix to the times shown (once a minute). Also, the number of bells sounded are shown (if any arguments are specified). If no arguments are specified, no times are shown. In all cases, the PC speaker is used to sound the bells (albeit a poorly sounded bell).

This REXX program makes use of DELAY BIF, which delays (sleeps) for a specified amount of seconds (some REXXes doen't have a DELAY BIF, so one is included here), and SOUND BIF, which produces sounds via the PC speaker (some REXXes doen't have a SOUND BIF, so one is included here). <lang rexx>/*REXX pgm sounds "bells" (using PC speaker) when running (perpetually).*/ echo= arg()\==0 /*echo time & bells if any args. */ signal on halt /*allow a clean way to stop prog.*/ t.1 = '00:30 01:00 01:30 02:00 02:30 03:00 03:30 04:00' t.2 = '04:30 05:00 05:30 06:00 06:30 07:00 07:30 08:00' t.3 = '08:30 09:00 09:30 10:00 10:30 11:00 11:30 12:00'

      do forever;  t=time();  ss=right(t,2);  mn=right(t,2)    /*times.*/
      ct=time('C')                              /*[↓] add leading zero.*/
      hhmmc=left( right( ct, 7, 0),  5)         /*HH:MM (leading zero).*/
      if echo  then say center(arg(1) ct, 79)   /*echo arg1 with time ?*/
      if ss\==00 & mn\==00 & mn\==30 then       /*wait for next min ?  */
        do;  call delay 60-ss;  iterate;  end   /*delay fraction of min*/

                                                /*[↓]  # bells to peel.*/
        do j=1 for 3  until $\==0;  $=wordpos(hhmmc,t.j);  end /*j*/

      if $\==0 & echo  then say center($ "bells", 79)    /*echo bells? */

        do k=1 for $; call sound 650,1; call delay 1+(k//2==0); end /*k*/
                                                /*[↑]   peel and pause.*/
      call delay 60                             /*ensure don't re-peel.*/
      end   /*forever*/

halt: /*stick a fork in it, we're done.*/</lang> output when using the input of: the time is:

                             the time is:   1:48pm
                             the time is:   1:49pm
                             the time is:   1:50pm
                             the time is:   1:51pm
                             the time is:   1:52pm
                             the time is:   1:53pm
                             the time is:   1:54pm
                             the time is:   1:55pm
                             the time is:   1:56pm
                             the time is:   1:57pm
                             the time is:   1:58pm
                             the time is:   1:59pm
                             the time is:   2:00pm
                                    4 bells
                             the time is:   2:01pm
                             the time is:   2:02pm
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