3 files changed, 44 insertions, 0 deletions
diff --git a/challenge-159/wlmb/blog.txt b/challenge-159/wlmb/blog.txt
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+++ b/challenge-159/wlmb/blog.txt
@@ -0,0 +1 @@
+https://wlmb.github.io/2022/04/05/PWC159/
diff --git a/challenge-159/wlmb/perl/ch-1.pl b/challenge-159/wlmb/perl/ch-1.pl
new file mode 100755
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+++ b/challenge-159/wlmb/perl/ch-1.pl
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+#!/usr/bin/env perl
+# Perl weekly challenge 159
+# Task 1: Farey sequence
+#
+# See https://wlmb.github.io/2022/04/05/PWC159/#task-1-farey-sequence
+use v5.12;
+use warnings;
+use POSIX qw(floor);
+use Text::Wrap qw(wrap $columns $break);
+die "Usage: ./ch-1.pl N1 [N2... ]\n to print Farey sequences of order N1, N2..." unless @ARGV;
+for(@ARGV){
+    my @farey=([0,1],[1,$_]);
+    while($farey[-1][1]!=1){
+        my ($a,$b,$c,$d)=(@{$farey[-2]}, @{$farey[-1]});
+        my $k=floor(($_+$b)/$d);
+	push @farey, [$k*$c-$a, $k*$d-$b];
+    }
+    $columns=62; $break=qr/\s/;
+    say "Input: $_\n",wrap("", "        ", "Output: ",
+	join ", ",
+	map {"$_->[0]/$_->[1]"} @farey);
+}
diff --git a/challenge-159/wlmb/perl/ch-2.pl b/challenge-159/wlmb/perl/ch-2.pl
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+++ b/challenge-159/wlmb/perl/ch-2.pl
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+#!/usr/bin/env perl
+# Perl weekly challenge 159
+# Task 2: Moebius number
+#
+# See https://wlmb.github.io/2022/04/05/PWC159/#task-2-moebius-number
+use v5.12;
+use warnings;
+use PDL;
+use PDL::NiceSlice;
+die "Usage: ./ch-2.pl N1 [N2... ]\n to find the Moebius numbers of N1, N2..." unless @ARGV;
+for(@ARGV){
+    my $sieve=ones($_+1); # Eratosthenes sieve
+    $sieve(0:1).=0;
+    $sieve($_**2:-1:$_).=0 for(2..sqrt($_)); # 1=prime, 0=nonprime
+    my $primes=$sieve->xvals->where($sieve); # primes
+    my $factors=$primes->where($_%$primes==0); # prime factors
+    my $prod=$factors->prodover; # product of factors, once each
+    my $square_free=$prod==$_;
+    my $parity=$factors->nelem%2?-1:1;
+    say "Input: $_ Output: ", $square_free?$parity:0;
+}