Task 2 plperl

1 files changed, 57 insertions, 0 deletions

diff --git a/challenge-159/luca-ferrari/postgresql/ch-2.plperl b/challenge-159/luca-ferrari/postgresql/ch-2.plperl
new file mode 100644
index 0000000000..8dce608e5a
--- /dev/null
+++ b/challenge-159/luca-ferrari/postgresql/ch-2.plperl
@@ -0,0 +1,57 @@
+CREATE SCHEMA IF NOT EXISTS pwc159;
+
+/**
+testdb=> select pwc159.mobius( 5 );
+ mobius 
+--------
+     -1
+(1 row)
+
+*/
+CREATE OR REPLACE FUNCTION
+pwc159.mobius( int )
+RETURNS int
+AS $CODE$
+
+   my ( $n ) = @_;
+
+   # a routine to compute the prime
+   # factors of the given number
+   my $prime_factors = sub {
+      my ( $number ) = @_;
+      my %factors;
+
+      my $factor = 2;
+      while (  $number > 1 && $factor <= $number ) {
+            if ( $number % $factor == 0 ) {
+               $factors{ $factor }++;
+               $number /= $factor;
+            }
+            else {
+                 $factor++;
+            }
+      }
+
+      return %factors;
+   };
+
+
+   my %prime_factors = $prime_factors->( $n );
+
+   # to get the unique prime factors I have to "count"
+   # them only once per key
+   my @unique_prime_factors;
+   my $occurrencies_prime_factors = 0;
+   for ( keys %prime_factors ) {
+       push @unique_prime_factors, $_;
+       $occurrencies_prime_factors += $prime_factors{ $_ };
+   }
+
+
+   return 0 if @unique_prime_factors != $occurrencies_prime_factors;
+   return 1 if @unique_prime_factors % 2 == 0;
+   return -1;
+
+
+$CODE$
+LANGUAGE plperl;