I am back from my vacations, I was at nice places in Switzerland like Rhone Glacier, underground lake of Saint-Leonard, Salt Mines of Bex, Rhine Waterfalls and more …
To keep up with the fun, here is a little quiz :
You have the numbers 1-3-4-6 and you need to achieve the number 24. The allowed operations are +, -, * and /
If I try to achieve 49 it is easy :
SQL> /
Enter value for n1: 1
old 14: (SELECT &n1 n
new 14: (SELECT 1 n
Enter value for n2: 3
old 17: SELECT &n2 n
new 17: SELECT 3 n
Enter value for n3: 4
old 20: SELECT &n3 n
new 20: SELECT 4 n
Enter value for n4: 6
old 23: SELECT &n4 n
new 23: SELECT 6 n
Enter value for result: 49
old 143: ) = &result
new 143: ) = 49
result
------------------------------------
(4+3)*(6+1)
(3+4)*(6+1)
(6+1)*(4+3)
(1+6)*(4+3)
(6+1)*(3+4)
(1+6)*(3+4)
(4+3)*(1+6)
(3+4)*(1+6)
8 rows selected.
Elapsed: 00:00:11.28But for 24 it is not that simple 
at least for human !
Ok, in SQL I am using a plsql function to evaluate expression
CREATE OR REPLACE FUNCTION lsc_eval (expr VARCHAR2)
RETURN NUMBER
IS
x NUMBER;
BEGIN
EXECUTE IMMEDIATE 'begin :x := ' || expr || ';end;'
USING OUT x;
RETURN x;
EXCEPTION
WHEN OTHERS
THEN
RETURN NULL;
END;
/
I will post the rest of the code as a comment later 
