From cb6b797384f6e8891dc8f4c71685fcb7a1a4e8a6 Mon Sep 17 00:00:00 2001
From: Luca Ferrari <fluca1978@gmail.com>
Date: Mon, 20 Dec 2021 16:13:46 +0100
Subject: Task 1 PostgreSQL done

---
 challenge-144/luca-ferrari/postgresql/ch-1.sql | 71 ++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 challenge-144/luca-ferrari/postgresql/ch-1.sql

diff --git a/challenge-144/luca-ferrari/postgresql/ch-1.sql b/challenge-144/luca-ferrari/postgresql/ch-1.sql
new file mode 100644
index 0000000000..c8d7264e7c
--- /dev/null
+++ b/challenge-144/luca-ferrari/postgresql/ch-1.sql
@@ -0,0 +1,71 @@
+/*
+ * Check if the current number is prime
+ */
+CREATE OR REPLACE FUNCTION f_is_prime( n int )
+RETURNS bool
+AS $CODE$
+DECLARE
+        divisor int;
+BEGIN
+        FOR divisor IN 2 .. ( n - 1 ) LOOP
+            IF mod( n, divisor ) = 0 THEN
+               RETURN false;
+            END IF;
+        END LOOP;
+
+        RETURN TRUE;
+END
+$CODE$
+LANGUAGE plpgsql;
+
+CREATE OR REPLACE FUNCTION f_semiprime_factors( n int )
+RETURNS SETOF int
+AS $CODE$
+DECLARE
+        current_number int;
+BEGIN
+        FOR current_number IN 1 .. n LOOP
+            IF f_is_prime( current_number ) AND mod( n, current_number ) = 0 AND f_is_prime(  ( n / current_number ) ) THEN
+               RETURN NEXT current_number;
+            END IF;
+        END LOOP;
+
+        RETURN;
+END
+$CODE$
+LANGUAGE plpgsql;
+
+
+
+CREATE OR REPLACE FUNCTION f_is_semiprime( n int )
+RETURNS bool
+AS $CODE$
+   SELECT CASE count( * )
+          WHEN 0 THEN false
+          ELSE true
+          END
+          FROM f_semiprime_factors( n ) s;
+$CODE$
+LANGUAGE sql;
+
+
+
+CREATE OR REPLACE FUNCTION f_find_semiprimes( lim int default 100 )
+RETURNS SETOF int
+AS $CODE$
+DECLARE
+      n int;
+BEGIN
+   n := 1;
+
+   WHILE n < lim LOOP
+       IF f_is_semiprime( n ) THEN
+          RETURN NEXT n;
+       END IF;
+       n := n + 1;
+   END LOOP;
+
+   RETURN;
+END
+$CODE$
+LANGUAGE plpgsql;
-- 
cgit