imported my attempts this week (2 very simple tasks)

3 files changed, 149 insertions, 47 deletions

diff --git a/challenge-108/duncan-c-white/README b/challenge-108/duncan-c-white/README
index 4073520658..5b35941c97 100644
--- a/challenge-108/duncan-c-white/README
+++ b/challenge-108/duncan-c-white/README
@@ -1,65 +1,56 @@
-Task 1: "Self-descriptive Numbers
+Task 1: "Locate Memory
 
-Write a script to display the first three self-descriptive numbers. As per wikipedia, the definition of Self-descriptive Number is
-
-    In mathematics, a self-descriptive number is an integer m that in a
-    given base b is b digits long in which each digit d at position n (the
-    most significant digit being at position 0 and the least significant
-    at position b-1) counts how many instances of digit n are in m.
-
-For example:
-
- 1210 is a four-digit self-descriptive number:
+Write a script to declare a variable or constant and print it's location in
+the memory.
+"
 
-    position 0 has value 1 i.e. there is only one 0 in the number
-    position 1 has value 2 i.e. there are two 1 in the number
-    position 2 has value 1 i.e. there is only one 2 in the number
-    position 3 has value 0 i.e. there is no 3 in the number
+My notes: umm, does this just mean "use \ and %p", or something more subtle?
 
-Output
 
-    1210, 2020, 21200
+Task 2: "Bell Numbers
 
-WARNING: I realised just before the launch this task was also part of the week
-43 and contributed by Laurent Rosenfeld. It is too late to change now. Feel
-free to share your previous solutions if you took part in the week 43
-already. I should have been more carefull, sorry.
-"
+Write a script to display top 10 Bell Numbers. Please refer to
 
-My notes: well, as it happened I skipped task 43, so let's have a go.  The
-important thing is: number of digits == base, which puts extra constraints
-on the digits.  So try bases b = 2.. try all base b numbers for "self-
-descriptiveness" and then and stop after finding the first N self-descriptive
-numbers.  Let's take N as a command line input for generality, default 3.
+https://en.wikipedia.org/wiki/Bell_number
 
+for more informations.
 
-Task 2: "List Methods
+Example:
 
-Write a script to list methods of a package/class.
+B0: 1 as you can only have one partition of zero element set
 
-Example
+B1: 1 as you can only have one partition of one element set {a}.
 
-package Calc;
+B2: 2
 
-use strict;
-use warnings;
+   {a}{b}
+   {a,b}
 
-sub new { bless {}, shift; }
-sub add { }
-sub mul { }
-sub div { }
+B3: 5
 
-1;
+   {a}{b}{c}
+   {a,b}{c}
+   {a}{b,c}
+   {a,c}{b}
+   {a,b,c}
 
-Output
+B4: 15
 
-BEGIN
-mul
-div
-new
-add
+   {a}{b}{c}{d}
+   {a,b,c,d}
+   {a,b}{c,d}
+   {a,c}{b,d}
+   {a,d}{b,c}
+   {a,b}{c}{d}
+   {a,c}{b}{d}
+   {a,d}{b}{c}
+   {b,c}{a}{d}
+   {b,d}{a}{c}
+   {c,d}{a}{b}
+   {a}{b,c,d}
+   {b}{a,c,d}
+   {c}{a,b,d}
+   {d}{a,b,c}
 "
 
-My notes: hmm, introspection.  I genuinely can't remember how to do this
-without a but of googling.  Isn't there a symbol table hash per package,
-that Memoize manipulates?  Ah yes: the stash containing typeglobs.
+My notes: Bell's triangle has a simple algorithm; let's use that!
diff --git a/challenge-108/duncan-c-white/perl/ch-1.pl b/challenge-108/duncan-c-white/perl/ch-1.pl
new file mode 100755
index 0000000000..1ee86d1354
--- /dev/null
+++ b/challenge-108/duncan-c-white/perl/ch-1.pl
@@ -0,0 +1,21 @@
+#!/usr/bin/perl
+# 
+# Task 1: "Locate Memory
+# 
+# Write a script to declare a variable or constant and print it's location in
+# the memory.
+# "
+# 
+# My notes: umm, does this just mean "use \ and %p", or something more subtle?
+# 
+
+use strict;
+use warnings;
+use feature 'say';
+use Data::Dumper;
+
+die "Usage: locate-memory val\n" unless @ARGV==1;
+
+my $x = shift;
+my $refx = \$x;
+printf "address of $x is %p\n", $refx;
diff --git a/challenge-108/duncan-c-white/perl/ch-2.pl b/challenge-108/duncan-c-white/perl/ch-2.pl
new file mode 100755
index 0000000000..ab4a11a674
--- /dev/null
+++ b/challenge-108/duncan-c-white/perl/ch-2.pl
@@ -0,0 +1,90 @@
+#!/usr/bin/perl
+# 
+# Task 2: "Bell Numbers
+# 
+# Write a script to display top 10 Bell Numbers. Please refer to
+# 
+# https://en.wikipedia.org/wiki/Bell_number
+# 
+# for more informations.
+# 
+# Example:
+# 
+# B0: 1 as you can only have one partition of zero element set
+# 
+# B1: 1 as you can only have one partition of one element set {a}.
+# 
+# B2: 2
+# 
+#    {a}{b}
+#    {a,b}
+# 
+# B3: 5
+# 
+#    {a}{b}{c}
+#    {a,b}{c}
+#    {a}{b,c}
+#    {a,c}{b}
+#    {a,b,c}
+# 
+# B4: 15
+# 
+#    {a}{b}{c}{d}
+#    {a,b,c,d}
+#    {a,b}{c,d}
+#    {a,c}{b,d}
+#    {a,d}{b,c}
+#    {a,b}{c}{d}
+#    {a,c}{b}{d}
+#    {a,d}{b}{c}
+#    {b,c}{a}{d}
+#    {b,d}{a}{c}
+#    {c,d}{a}{b}
+#    {a}{b,c,d}
+#    {b}{a,c,d}
+#    {c}{a,b,d}
+#    {d}{a,b,c}
+# "
+# 
+# My notes: Bell's triangle has a simple algorithm; let's use that!
+# 
+
+use strict;
+use warnings;
+use feature 'say';
+use Function::Parameters;
+use Getopt::Long;
+use Data::Dumper;
+
+my $debug = 0;
+die "Usage: bells-numbers [--debug] N\n"
+	unless GetOptions("debug"=>\$debug) && @ARGV<2;
+
+my $n = shift // 10;
+
+my @bell = first_n_bell_nos( $n );
+say join( ',', @bell );
+
+#
+# my @bell = first_n_bell_nos( $n );
+#	Generate and return the first $n bell numbers.
+#
+fun first_n_bell_nos( $n )
+{
+	my @result;
+	my @currrow = (1);
+	push @result, $currrow[0];
+	foreach my $i (1..$n-1)
+	{
+		my @nextrow;
+		$nextrow[0] = $currrow[-1];
+		foreach my $j (1..$i)
+		{
+			$nextrow[$j] = $currrow[$j-1] + $nextrow[$j-1];
+		}
+		say join( ' ', @nextrow ) if $debug;
+		push @result, $nextrow[0];
+		@currrow = @nextrow;
+	}
+	return @result;
+}