1 files changed, 69 insertions, 0 deletions
diff --git a/challenge-159/luca-ferrari/postgresql/ch-1.sql b/challenge-159/luca-ferrari/postgresql/ch-1.sql
index da8824c0c2..1ebd6c5112 100644
--- a/challenge-159/luca-ferrari/postgresql/ch-1.sql
+++ b/challenge-159/luca-ferrari/postgresql/ch-1.sql
@@ -1 +1,70 @@
 -- Perl Weekly Challenge 159
+
+
+CREATE SCHEMA IF NOT EXISTS pwc159;
+
+
+CREATE OR REPLACE FUNCTION
+pwc159.farey_not_unique( n int )
+RETURNS TABLE( f text, v numeric )
+AS $CODE$
+DECLARE
+     numerator   int;
+     denominator int;
+     dd          int;
+     nn          int;
+BEGIN
+
+        -- bootstrap term
+        SELECT '0/1', 0
+        INTO f, v;
+
+        RETURN NEXT;
+
+
+        FOR denominator IN 2 .. n  LOOP
+            FOR numerator IN  1 .. denominator  LOOP
+                nn := numerator;
+                dd := denominator;
+
+                IF dd % nn = 0 THEN
+                   dd := dd / nn;
+                   nn := 1;
+                END IF;
+
+                IF nn % dd = 0 THEN
+                   nn := nn / dd;
+                   dd := 1;
+                END IF;
+
+                IF nn / dd = 1 THEN
+                   CONTINUE;
+                END IF;
+
+                SELECT nn || '/' || dd, nn/dd::numeric
+                INTO  f, v;
+
+                RETURN NEXT;
+
+            END LOOP;
+        END LOOP;
+
+        -- end term
+        SELECT '1/1', 1
+        INTO f, v;
+
+        RETURN NEXT;
+
+RETURN;
+END
+$CODE$
+LANGUAGE plpgsql;
+
+
+WITH farey AS (
+     SELECT distinct( f ), v
+     FROM pwc159.farey_not_unique( 5 )
+     ORDER BY v
+)
+SELECT f
+FROM farey;