Solutions to challenge 078

2 files changed, 48 insertions, 0 deletions

diff --git a/challenge-078/jo-37/perl/ch-1.pl b/challenge-078/jo-37/perl/ch-1.pl
new file mode 100755
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+++ b/challenge-078/jo-37/perl/ch-1.pl
@@ -0,0 +1,22 @@
+#!/usr/bin/perl
+
+use Test2::V0;
+use List::Util 'reduce';
+
+# Viewing at the array from right to left.  Every element that is larger
+# than the current first leading element is leading too and is prepended
+# to the list.  Appending (0) to an empty list as requested, though this
+# leads to ambiguous results.
+sub leading {
+	(@{(reduce {
+		unshift @$a, $b if $b > ($a->[0] // '-inf');
+		$a;
+	} [], reverse @_)}, (0) x !@_) ;
+}
+
+is [leading 9, 10, 7, 5, 6, 1], [10, 7, 6, 1], 'first example'; 
+is [leading 3, 4, 5], [5], 'second example';
+is [leading], [0], 'no leader';
+is [leading -1, 0], [0], 'ambiguous result';
+
+done_testing;
diff --git a/challenge-078/jo-37/perl/ch-2.pl b/challenge-078/jo-37/perl/ch-2.pl
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+++ b/challenge-078/jo-37/perl/ch-2.pl
@@ -0,0 +1,26 @@
+#!/usr/bin/perl
+
+use PDL;
+# avoid conflicting import
+use Test2::V0 '!float';
+
+sub multi_rotate {
+	# convert 1st arg to a piddle
+	my $a = long(shift);
+	# 2nd arg: pack the array elements into arrays of length one.
+	my $b = [map [$_], @{(shift)}];
+
+	# The range method returns rectangular parts of the input piddle
+	# starting at the given positions.  With the full length of $a as
+	# the parts' length and periodic boundary conditions it actually
+	# performs multiple rotations just as required by this task.  The
+	# source dimension needs to be moved to the front.
+	$a->range($b, $a->dim(0), 'periodic')->reorder(1, 0)->unpdl;
+}
+
+is multi_rotate([10, 20, 30, 40, 50], [3, 4]),
+	[[40, 50, 10, 20, 30], [50, 10, 20, 30, 40]], 'first example';
+is multi_rotate([7, 4, 2, 6, 3], [1, 3, 4]),
+	[[4, 2, 6, 3, 7], [6, 3, 7, 4, 2], [3, 7, 4, 2, 6]], 'second example';
+
+done_testing;