- Added solutions by Duane Powell.

2 files changed, 118 insertions, 0 deletions

diff --git a/challenge-021/duane-powell/perl5/ch-1.pl b/challenge-021/duane-powell/perl5/ch-1.pl
new file mode 100644
index 0000000000..eee3e3a3df
--- /dev/null
+++ b/challenge-021/duane-powell/perl5/ch-1.pl
@@ -0,0 +1,77 @@
+#!/usr/bin/perl
+use Modern::Perl;
+use bignum qw(e);
+use Math::BigFloat;
+Math::BigFloat->precision(-50);
+
+# write a script to calculate e https://en.wikipedia.org/wiki/E_(mathematical_constant)
+# e, Euler's number, 2.71828182845904523536028747135266249775724709369995
+
+sub factorial {
+	my $f = 1;
+	map { $f *= $_ } ( 1 .. shift );  
+	return $f;
+}
+
+sub e_factorial {
+	my $e = 0;
+	map { $e += 1/factorial($_) } ( 0 .. shift );
+	return $e;
+}
+
+sub brothers {
+	my $b = 0; 
+	map { $b += (2 * $_ + 2) / factorial(2 * $_ + 1) } ( 0 .. shift );
+	return $b;
+}
+
+sub e_brothers {
+	my $b = shift;
+	my $e = brothers($b);
+	return $e;
+}
+
+sub e_limit_n {
+	my $n = shift;
+	return ( 1 + 1/$n ) ** $n;
+}
+
+sub e_limit_t {
+	my $t = shift;
+	return ( 1 + $t ) ** (1/$t);
+}
+
+
+my $e = 2.71828182845904523536028747135266249775724709369995;
+say $e, " e constant from wiki";
+
+$e = e(); 
+say $e, " e from perl module bignum";
+
+my $n = 40;
+$e = e_factorial($n);
+say $e, " e calculated from $n factorial";
+
+$n = 20;
+$e = e_brothers($n);
+say $e, " e calculated from brothers, $n steps";
+
+$n = 100000;
+$e = e_limit_n($n);
+say $e, " e calculated as a limit n approaching infinity $n";
+
+$n = .00001;
+$e = e_limit_t($n);
+say $e, " e calculated as a limit t approaching zero $n";
+
+
+__END__
+
+./ch1.pl
+2.71828182845904523536028747135266249775724709369995 e constant from wiki
+2.71828182845904523536028747135266249775700000000000 e from perl module bignum
+2.71828182845904523536028747135266249775724709369992 e calculated from 40 factorial
+2.71828182845904523536028747135266249775724709369997 e calculated from brothers, 20 steps
+2.71826823717448966803506482442604644797444693267782 e calculated as a limit n approaching infinity 100000
+2.71826823717448966803506482442604644797444693267782 e calculated as a limit t approaching zero 0.00001
+
diff --git a/challenge-021/duane-powell/perl5/ch-2.pl b/challenge-021/duane-powell/perl5/ch-2.pl
new file mode 100644
index 0000000000..fccd7934d9
--- /dev/null
+++ b/challenge-021/duane-powell/perl5/ch-2.pl
@@ -0,0 +1,41 @@
+#!/usr/bin/perl
+use Modern::Perl;
+use URI qw(canonical);
+
+# take a list of urls and say their normal forms
+
+my @url = qw(
+HTTP://www.Example.com/
+HTTP://www.example.COM:80/
+https://www.example.com/
+https://www.example.com:443/
+http://www.example.com/a%c2%b1b
+http://www.example.com/%7Eusername/
+http://www.example.com:80/bar.html
+);
+
+my %normal_url;
+foreach my $url (@url) {
+	push @{ $normal_url{ URI->new($url)->canonical() } }, $url;
+}
+
+foreach my $url ( sort {$a cmp $b} (keys %normal_url) ) {
+	say $url;
+	foreach ( sort {$a cmp $b} @{ $normal_url{$url} } ) {
+		say "\t$_";
+	}
+}
+
+__END__
+
+./ch2.pl
+http://www.example.com/
+        HTTP://www.Example.com/
+        http://www.example.com:80/
+http://www.example.com/a%C2%B1b
+        http://www.example.com/a%c2%b1b
+http://www.example.com/bar.html
+        http://www.example.com:80/bar.html
+http://www.example.com/~username/
+        http://www.example.com/%7Eusername/
+