Merge pull request #6382 from dcw803/master

imported my solutions to this week's tasks - 2 in Perl and 1 in C..

6 files changed, 250 insertions, 43 deletions

diff --git a/challenge-171/duncan-c-white/C/.build b/challenge-171/duncan-c-white/C/.cbuild
index 7a8295430e..7171ba4c65 100644
--- a/challenge-171/duncan-c-white/C/.build
+++ b/challenge-171/duncan-c-white/C/.cbuild
@@ -1,2 +1,3 @@
 BUILD = ch-1
+CFLAGS = -Wall
 #CFLAGS = -g
diff --git a/challenge-171/duncan-c-white/C/Makefile b/challenge-171/duncan-c-white/C/Makefile
new file mode 100644
index 0000000000..e14a397db5
--- /dev/null
+++ b/challenge-171/duncan-c-white/C/Makefile
@@ -0,0 +1,13 @@
+# Makefile rules generated by CB
+CC	= gcc
+CFLAGS	= -Wall
+BUILD	= ch-1
+
+all:	$(BUILD)
+
+clean:
+	/bin/rm -f $(BUILD) *.o core a.out
+
+ch-1:	ch-1.o
+ch-1.o:	ch-1.c
+
diff --git a/challenge-171/duncan-c-white/C/ch-1.c b/challenge-171/duncan-c-white/C/ch-1.c
new file mode 100644
index 0000000000..a102774c93
--- /dev/null
+++ b/challenge-171/duncan-c-white/C/ch-1.c
@@ -0,0 +1,107 @@
+/* 
+ * TASK 1 - Odd Abundant Numbers
+ * 
+ * GUEST LANGUAGE: THIS IS THE C VERSION OF ch-1.pl;
+ * I took the liberty of merging finding factors and summing them.
+ */ 
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+//#include <stdint.h>
+#include <string.h>
+#include <assert.h>
+#include <unistd.h>
+#include <ctype.h>
+
+
+bool debug=false;
+
+
+// int n = process_singlearg( name, argc, argv, def );
+//	Process the -d flag, and check that there is a single
+//	remaining argument (or return $def if there are no args),
+//	return that argument's numeric value.
+int process_singlearg( char *name, int argc, char **argv, int def )
+{
+	int arg=1;
+	if( argc>1 && strcmp( argv[arg], "-d" ) == 0 )
+	{
+		debug = true;
+		arg++;
+	}
+
+	int left = argc-arg;
+	if( left == 0 )
+	{
+		return def;		// default
+	}
+	if( left != 1 )
+	{
+		fprintf( stderr,
+			"Usage: %s [-d] firstN (default %d)\n", name, def );
+		exit(1);
+	}
+
+	// element is in argv[arg]
+
+	if( debug )
+	{
+		printf( "debug: remaining argument is in arg=%d, firstn=%s\n",
+			arg, argv[arg] );
+	}
+
+	return atoi( argv[arg] );
+}
+
+
+//
+// int sum_f = sum_factors_less_than_n( n );
+//	Find all the factors of n
+//	including 1 but less than n.
+//	Sum them all and return the sum.
+//
+int sum_factors_less_than_n( int n )
+{
+	int sumf = 0;
+	for( int i=1; i<n; i++ )
+	{
+		 if( n%i == 0 ) sumf += i;
+	}
+	return sumf;
+}
+
+
+int main( int argc, char **argv )
+{
+	int n = process_singlearg( "odd-abundant-nos", argc, argv, 20 );
+
+	int *oa;		// the first n Odd Abundant numbers
+	oa = malloc( n * sizeof(int) );
+	int noa = 0;
+
+	for( int i = 3; noa<n; i+=2 )
+	{
+		int sum = sum_factors_less_than_n( i );
+		if( debug )
+		{
+			printf( "i=%d, sum=%d\n", i, sum );
+		}
+		if( sum > i )
+		{
+			if( debug )
+			{
+				printf( "found odd abdundant no %d\n", i );
+			}
+			oa[noa++] = i;
+		}
+	}
+
+	for( int i=0; i<noa; i++ )
+	{
+		printf( "%d\n", oa[i] );
+	}
+
+	free( oa );
+	return 0;
+}
diff --git a/challenge-171/duncan-c-white/README b/challenge-171/duncan-c-white/README
index c46a4e6435..755694b9fc 100644
--- a/challenge-171/duncan-c-white/README
+++ b/challenge-171/duncan-c-white/README
@@ -1,57 +1,33 @@
-TASK 1: Primorial Numbers
+Task 1: Abundant Number
 
-Write a script to generate first 10 Primorial Numbers:
-Primorial numbers are those formed by multiplying successive prime numbers.
+Write a script to generate first 20 Abundant Odd Numbers.
 
-For example,
+According to wikipedia: A number n for which the sum of proper divisors
+(divisors from 1 but less than n) s(n) > n.
 
-P(0) = 1    (1)
-P(1) = 2    (1x2)
-P(2) = 6    (1x2x3)
-P(3) = 30   (1x2x3x5)
+For example, 945 is the first Abundant Odd Number.
 
-MY NOTES: ok, sounds easy, but I'm getting very bored of
-"tasks to do with Number Theory and (especially) Primes".
+Sum of divisors:
+1 + 3 + 5 + 7 + 9 + 15 + 21 + 27 + 35 + 45 + 63 + 105 + 135 + 189 + 315 = 975
+
+MY NOTES: ok, sounds easy, and at least it's nowt to do with Primes:-)
 
 GUEST LANGUAGE: As a bonus, I also had a go at translating ch-1.pl
 into C (look in the C directory for that).
 
 
-Task 2: Kronecker Product
-
-You are given 2 matrices.
-
-Write a script to implement Kronecker Product on the given 2 matrices.
-
-For more information, please refer to the wikipedia page
-https://en.wikipedia.org/wiki/Kronecker_product
+Task 2: First-class Function
 
-For example,
+Create sub compose($f, $g) which takes in two parameters $f and $g as
+subroutine refs and returns subroutine ref i.e. compose($f, $g)->($x)
+= $f->($g->($x))
 
-A = [ 1 2 ]
-    [ 3 4 ]
+e.g.
 
-B = [ 5 6 ]
-    [ 7 8 ]
+$f = (one or more parameters function)
+$g = (one or more parameters function)
 
-A x B = [ 1 x [ 5 6 ]   2 x [ 5 6 ] ]
-        [     [ 7 8 ]       [ 7 8 ] ]
-        [ 3 x [ 5 6 ]   4 x [ 5 6 ] ]
-        [     [ 7 8 ]       [ 7 8 ] ]
+$h = compose($f, $g)
+$f->($g->($x,$y, ..)) == $h->($x, $y, ..) for any $x, $y, ...
 
-      = [ 1x5 1x6 2x5 2x6 ]
-        [ 1x7 1x8 2x7 2x8 ]
-        [ 3x5 3x6 4x5 4x6 ]
-        [ 3x7 3x8 4x7 4x8 ]
-
-      = [  5  6 10 12 ]
-        [  7  8 14 16 ]
-        [ 15 18 20 24 ]
-        [ 21 24 28 32 ]
-
-MY NOTES: Ok, at least it has nothing to do with prime numbers:-)
-I note in the Wikipedia page the useful formula:
-(A x B)ij = Ai/p,j/q * Bi%p,j%q    [where B is of size p x q]
-
-GUEST LANGUAGE: As a bonus, I also had a go at translating ch-2.pl
-into C (look in the C directory for that).
+MY NOTES: An interesting question at last.  Think it's quite easy..
diff --git a/challenge-171/duncan-c-white/perl/ch-1.pl b/challenge-171/duncan-c-white/perl/ch-1.pl
new file mode 100755
index 0000000000..73a5519592
--- /dev/null
+++ b/challenge-171/duncan-c-white/perl/ch-1.pl
@@ -0,0 +1,62 @@
+#!/usr/bin/perl
+# 
+# Task 1: Abundant Number
+# 
+# Write a script to generate first 20 Abundant Odd Numbers.
+# 
+# According to wikipedia: A number n for which the sum of proper divisors
+# (divisors from 1 but less than n) s(n) > n.
+# 
+# For example, 945 is the first Abundant Odd Number.
+# 
+# Sum of divisors:
+# 1 + 3 + 5 + 7 + 9 + 15 + 21 + 27 + 35 + 45 + 63 + 105 + 135 + 189 + 315 = 975
+# 
+# MY NOTES: ok, sounds easy, and at least it's nowt to do with Primes:-)
+#
+# GUEST LANGUAGE: As a bonus, I also had a go at translating ch-1.pl
+# into C (look in the C directory for that).
+# 
+
+use strict;
+use warnings;
+use feature 'say';
+use Getopt::Long;
+use Data::Dumper;
+use List::Util qw(sum0);
+
+my $debug=0;
+die "Usage: odd-abundant-numbers [--debug] [N default 20]\n"
+	unless GetOptions( "debug"=>\$debug ) && @ARGV<2;
+my $n = shift // 20;
+
+#
+# my @f = factors_less_than_n( $n );
+#	Find and return an array of all the factors of $n
+#	including 1 but less than $n.
+#
+sub factors_less_than_n
+{
+	my( $n ) = @_;
+	my @f;
+	for( my $i=1; $i<$n; $i++ )
+	{
+		push @f, $i if $n%$i==0;
+	}
+	return @f;
+}
+
+
+my @oa;		# the first few Odd Abundant numbers we find
+
+for( my $i = 3; @oa<$n; $i+=2 )
+{
+	my @f = factors_less_than_n( $i );
+	my $sum = sum0(@f);
+	say "i=$i, factors = ". join(',',@f). ", sum=$sum" if $debug;
+	next if $sum <= $i;
+	say "found odd abdundant no $i" if $debug;
+	push @oa, $i;
+}
+
+say for @oa;
diff --git a/challenge-171/duncan-c-white/perl/ch-2.pl b/challenge-171/duncan-c-white/perl/ch-2.pl
new file mode 100755
index 0000000000..2fcb8c2360
--- /dev/null
+++ b/challenge-171/duncan-c-white/perl/ch-2.pl
@@ -0,0 +1,48 @@
+#!/usr/bin/perl
+# 
+# Task 2: First-class Function
+# 
+# Create sub compose($f, $g) which takes in two parameters $f and $g as
+# subroutine refs and returns subroutine ref i.e. compose($f, $g)->($x)
+# = $f->($g->($x))
+# 
+# e.g.
+# 
+# $f = (one or more parameters function)
+# $g = (one or more parameters function)
+# 
+# $h = compose($f, $g)
+# $f->($g->($x,$y, ..)) == $h->($x, $y, ..) for any $x, $y, ...
+# 
+# MY NOTES: An interesting question at last.  Think it's quite easy..
+# 
+
+use strict;
+use warnings;
+use feature 'say';
+use Getopt::Long;
+use Function::Parameters;
+use Data::Dumper;
+use List::Util qw(sum0);
+
+my $debug=0;
+die "Usage: first-class-function [--debug] ARGS FOR FUNCS\n"
+	unless GetOptions( "debug"=>\$debug ) && @ARGV>0;
+
+#
+# my $fg = compose( $f, $g );
+#	Higher order function composer.  Return a newly minted
+#	composed function (subroutine ref) that, when called, applies
+#	$f first, then $g.
+#
+fun compose( $f, $g )
+{
+	return fun(@x) { return $f->($g->(@x)); }
+}
+
+
+my $sum       = fun( @x ) { return sum0(@x); };
+my $double    = fun( @x ) { return map { 2 * $_ } @x };
+my $sumdouble = compose( $sum, $double );
+my $n = $sumdouble->( @ARGV );
+say $n;