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/*
testdb=> select * from f_lychrel( 59, true );
INFO: Found 1111 after 3 iterations
f_lychrel
-----------
0
*/
CREATE OR REPLACE FUNCTION
f_lychrel( n int, verb boolean default false )
RETURNS smallint
AS $CODE$
DECLARE
result bigint := n;
iteration int := 0;
BEGIN
IF n < 10 OR n > 10000 THEN
RAISE 'n is out of bounds!';
END IF;
WHILE result < 10000000 AND iteration < 500 LOOP
iteration = iteration + 1;
result = result + reverse( result::text )::int;
IF result = reverse( result::text )::int THEN
IF verb THEN
RAISE INFO 'Found % after % iterations', result, iteration;
END IF;
RETURN 0;
END IF;
END LOOP;
RETURN 1;
END
$CODE$
LANGUAGE plpgsql;
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