From b687fe1babaa737f2d4d409338262c2f9ad1618c Mon Sep 17 00:00:00 2001
From: Alexander Pankoff <ccntrq@screenri.de>
Date: Tue, 8 Dec 2020 13:39:52 +0100
Subject: add solutions for challenge-090 in perl

---
 challenge-090/alexander-pankoff/perl/ch-1.pl | 17 ++++++++++++++
 challenge-090/alexander-pankoff/perl/ch-2.pl | 34 ++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)
 create mode 100755 challenge-090/alexander-pankoff/perl/ch-1.pl
 create mode 100755 challenge-090/alexander-pankoff/perl/ch-2.pl

diff --git a/challenge-090/alexander-pankoff/perl/ch-1.pl b/challenge-090/alexander-pankoff/perl/ch-1.pl
new file mode 100755
index 0000000000..15f2c016bc
--- /dev/null
+++ b/challenge-090/alexander-pankoff/perl/ch-1.pl
@@ -0,0 +1,17 @@
+#!/usr/bin/env perl
+use v5.20;
+use utf8;
+use strict;
+use warnings;
+use feature qw(say signatures);
+no warnings 'experimental::signatures';
+
+{
+    my ( $sequence ) = @ARGV;
+    die 'need dna sequence' unless $sequence;
+    my %complements = ( T => 'A', G => 'C' );
+    %complements = ( %complements, reverse %complements );
+
+    say 'Nucleiobase count: ' . length( $sequence );
+    say 'Complementary sequence: ' . join( '', map { $complements{$_} } split( '', $sequence ) );
+}
diff --git a/challenge-090/alexander-pankoff/perl/ch-2.pl b/challenge-090/alexander-pankoff/perl/ch-2.pl
new file mode 100755
index 0000000000..51f636cc6f
--- /dev/null
+++ b/challenge-090/alexander-pankoff/perl/ch-2.pl
@@ -0,0 +1,34 @@
+#!/usr/bin/env perl
+use v5.20;
+use utf8;
+use strict;
+use warnings;
+use feature qw(say signatures);
+no warnings 'experimental::signatures';
+
+use List::Util qw(sum0);
+
+use Test::Simple tests => 20;
+
+{
+    for ( 0 .. 19 ) {
+        my ( $a, $b ) = map { int( rand( 1000 ) ) + 1 } 0 .. 1;
+        my $expected = $a * $b;
+        ok( ethopian_mul( $a, $b ) == $expected, "ethopian_mul($a, $b) = $a * $b = $expected" );
+    }
+}
+
+sub ethopian_mul ( $a, $b ) {
+    return sum0( map { $_->[1] } grep { odd( $_->[0] ) } ethopian_mul_chain( $a, $b ) );
+}
+
+sub ethopian_mul_chain ( $a, $b ) {
+    return [ $a, $b ] if $a <= 1;
+
+    # using bit shifts to avoid use of multiplication
+    return ( [ $a, $b ], ethopian_mul_chain( $a >> 1, $b << 1 ) );
+}
+
+sub odd($x) {
+    $x != ( ( $x >> 1 ) << 1 );
+}
-- 
cgit 


From 958a003d916036a4f72aa87fa5a3d5ea2717d952 Mon Sep 17 00:00:00 2001
From: Alexander Pankoff <ccntrq@screenri.de>
Date: Tue, 8 Dec 2020 14:10:52 +0100
Subject: reimplement odd

---
 challenge-090/alexander-pankoff/perl/ch-2.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/challenge-090/alexander-pankoff/perl/ch-2.pl b/challenge-090/alexander-pankoff/perl/ch-2.pl
index 51f636cc6f..eb588779f8 100755
--- a/challenge-090/alexander-pankoff/perl/ch-2.pl
+++ b/challenge-090/alexander-pankoff/perl/ch-2.pl
@@ -30,5 +30,5 @@ sub ethopian_mul_chain ( $a, $b ) {
 }
 
 sub odd($x) {
-    $x != ( ( $x >> 1 ) << 1 );
+    $x & 1;
 }
-- 
cgit 


From 92d41f92a59d5ebad74d12edec19e86ad1d53aed Mon Sep 17 00:00:00 2001
From: Alexander Pankoff <ccntrq@screenri.de>
Date: Tue, 8 Dec 2020 14:11:00 +0100
Subject: add verbose mode

---
 challenge-090/alexander-pankoff/perl/ch-2.pl | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/challenge-090/alexander-pankoff/perl/ch-2.pl b/challenge-090/alexander-pankoff/perl/ch-2.pl
index eb588779f8..a66c4feea7 100755
--- a/challenge-090/alexander-pankoff/perl/ch-2.pl
+++ b/challenge-090/alexander-pankoff/perl/ch-2.pl
@@ -10,6 +10,8 @@ use List::Util qw(sum0);
 
 use Test::Simple tests => 20;
 
+use constant VERBOSE => $ENV{VERBOSE} // 0;
+
 {
     for ( 0 .. 19 ) {
         my ( $a, $b ) = map { int( rand( 1000 ) ) + 1 } 0 .. 1;
@@ -19,7 +21,16 @@ use Test::Simple tests => 20;
 }
 
 sub ethopian_mul ( $a, $b ) {
-    return sum0( map { $_->[1] } grep { odd( $_->[0] ) } ethopian_mul_chain( $a, $b ) );
+    my @chain = ethopian_mul_chain( $a, $b );
+    verbose( "halving $a, doubling $b, till $a becomes 1" );
+    verbose( $_->[0] . ' & ' . $_->[1] ) for @chain;
+
+    my @filtered = map { $_->[1] } grep { odd( $_->[0] ) } @chain;
+    verbose( "taking right values where left value is odd" );
+    verbose( $_ ) for @filtered;
+    my $product = sum0( @filtered );
+    verbose( "product is $product" );
+    return $product;
 }
 
 sub ethopian_mul_chain ( $a, $b ) {
-- 
cgit