move `combinations` from ch-083 into a module for reuse

2 files changed, 37 insertions, 20 deletions

diff --git a/challenge-083/alexander-pankoff/perl/ch-2.pl b/challenge-083/alexander-pankoff/perl/ch-2.pl
index 2e3ca72fca..116f701716 100755
--- a/challenge-083/alexander-pankoff/perl/ch-2.pl
+++ b/challenge-083/alexander-pankoff/perl/ch-2.pl
@@ -7,12 +7,16 @@ use autodie;
 use feature qw(say signatures);
 no warnings 'experimental::signatures';
 
-use Carp qw(croak);
 use List::Util qw(any first sum0);
 use Scalar::Util qw(looks_like_number);
 
 use Pod::Usage;
 
+use FindBin;
+use lib File::Spec->join( $FindBin::RealBin, 'lib' );
+
+use Combinations qw(combinations);
+
 pod2usage(
     -message => "$0: Expects a list of positive numbers",
     -exitval => 1,
@@ -38,25 +42,6 @@ sub flip_array(@numbers) {
     return 0;
 }
 
-# returns possible combinations of $length elements from @pool.
-sub combinations ( $count, @pool ) {
-    croak "cannot build combinations with $count elements from a list of "
-      . scalar(@pool)
-      . " elements"
-      if $count > @pool;
-    return ()                 if $count == 0;
-    return map { [$_] } @pool if $count == 1;
-
-    my @combinations;
-    while ( @pool && $count <= @pool ) {
-        my $elem             = shift @pool;
-        my @sub_combinations = combinations( $count - 1, @pool );
-        push @combinations, map { [ $elem, @$_, ] } @sub_combinations;
-    }
-
-    return @combinations;
-}
-
 =pod
 
 =head1 NAME
diff --git a/challenge-083/alexander-pankoff/perl/lib/Combinations.pm b/challenge-083/alexander-pankoff/perl/lib/Combinations.pm
new file mode 100644
index 0000000000..73b22cfa65
--- /dev/null
+++ b/challenge-083/alexander-pankoff/perl/lib/Combinations.pm
@@ -0,0 +1,32 @@
+package Combinations;
+use strict;
+use warnings;
+use feature qw(signatures);
+no warnings 'experimental::signatures';
+
+use Carp qw(croak);
+
+use Exporter qw(import);
+
+our @EXPORT_OK = qw(combinations);
+
+# returns possible combinations of $length elements from @pool.
+sub combinations ( $count, @pool ) {
+    croak "cannot build combinations with $count elements from a list of "
+      . scalar(@pool)
+      . " elements"
+      if $count > @pool;
+    return () if $count == 0;
+    return map { [$_] } @pool if $count == 1;
+
+    my @combinations;
+    while ( @pool && $count <= @pool ) {
+        my $elem = shift @pool;
+        my @sub_combinations = combinations( $count - 1, @pool );
+        push @combinations, map { [ $elem, @$_, ] } @sub_combinations;
+    }
+
+    return @combinations;
+}
+
+1;