Advent Calendar 2021

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The gift is presented by Roger Bell_West. Today he is talking about his solution to “The Weekly Challenge - 120”. This is re-produced for Advent Calendar 2021 from the original post by Roger Bell_West.

Task #2: Clock Angle

You are given time $T in the format hh:mm.

Write a script to find the smaller angle formed by the hands of an analog clock at a given time.

Which seems again as though it has a fairly straightforward solution: determine the angle of each hand, then reduce the difference.

Raku:

sub ca($n) {
  my $a=0;

Extract hour and minute:

  if ($n ~~ /(<[0..9]>+)\:(<[0..9]>+)/) {

Convert each one to an angle (note that each minute puts half a degree on the hour hand, so we’re in floating point territory):

    my ($ha,$ma)=map {$_ % 360}, ($0*30+$1/2,$1*6);

Take the absolute difference:

    $a=abs($ha-$ma);

Reduce until we get an angle lying in (-180..180):

    while ($a > 180) {
      $a-=360;
    }

And take the absolute again.

    $a=abs($a);
  }
  return $a;
}

The complete solution in Raku.

#! /usr/bin/perl6

use Test;

plan 2;

is(ca('03:10'),35,'example 1');
is(ca('04:00'),120,'example 2');

sub ca($n) {
  my $a=0;
  if ($n ~~ /(<[0..9]>+)\:(<[0..9]>+)/) {
    my ($ha,$ma)=map {$_ % 360}, ($0*30+$1/2,$1*6);
    $a=abs($ha-$ma);
    while ($a > 180) {
      $a-=360;
    }
    $a=abs($a);
  }
  return $a;
}

If you have any suggestion then please do share with us perlweeklychallenge@yahoo.com.

Advent Calendar 2021