my proposed solutions for challenge-026, p5 1 & 2

2 files changed, 57 insertions, 0 deletions

diff --git a/challenge-026/daniel-mantovani/perl5/ch-1.pl b/challenge-026/daniel-mantovani/perl5/ch-1.pl
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+++ b/challenge-026/daniel-mantovani/perl5/ch-1.pl
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+# Create a script that accepts two strings, let us call it, “stones” and “jewels”.
+# It should print the count of “alphabet” from the string “stones” found in the
+# string “jewels”. For example, if your stones is “chancellor” and “jewels” is
+# “chocolate”, then the script should print “8”. To keep it simple, only A-Z,a-z
+# characters are acceptable. Also make the comparison case sensitive.
+
+use strict;
+use warnings;
+use v5.20;
+
+# let's read the two strings from command line
+my ( $stones, $jewels ) = @ARGV;
+
+my $n = 0;
+
+# we just count the times each char from $stones exists in $jewels
+
+$n += $jewels =~ /$_/ for split '', $stones;
+
+# and I think that's it, unless I misunderstood the challenge (which is very likely)
+
+say "$stones letters found in $jewels are $n in total";
diff --git a/challenge-026/daniel-mantovani/perl5/ch-2.pl b/challenge-026/daniel-mantovani/perl5/ch-2.pl
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+++ b/challenge-026/daniel-mantovani/perl5/ch-2.pl
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+# Create a script that prints mean angles of the given list of angles in degrees.
+# Please read wiki page that explains the formula in details with an example.
+
+use strict;
+use warnings;
+use v5.20;
+
+# first we define constant pi as twice a 90 degrees angle:
+
+use constant PI => 2 * atan2( 1, 0 );
+
+# now we read angles list
+
+my @angles = @ARGV or die "Usage: perl $0 <list of angles in degrees>";
+
+# we are going to just add sines and cosines of each angle.
+# The wiki page actually asks to average them, but as we are going to calculate
+# an angle at the end, there is no difference with calculating it with the sums
+
+my ( $sins_sum, $coss_sum ) = ( 0, 0 );
+
+$sins_sum += sin( $_ * PI / 180 ) for @angles;
+$coss_sum += cos( $_ * PI / 180 ) for @angles;
+
+# There is a case when no circular mean exists, and it is when
+# all angles are uniformly distributed on the circle.
+# In that case, both $sins_sum and $coss_sum are 0
+# To avoid precision math errors, we will assume that when sum of
+# square of sum of sines and square of sum of cosines is less than
+# 1 / 1_000_000 means both are 0
+
+say $sins_sum * $sins_sum + $coss_sum * $coss_sum < 1e-6
+  ? 'No circular mean exists for given angles'
+  : sprintf( "Circular mean is: %.2f", 180 / PI * atan2 $sins_sum, $coss_sum );
+