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CREATE OR REPLACE FUNCTION
f_long_primes( l int default 5 )
RETURNS SETOF bigint
AS $CODE$
DECLARE
current_value numeric;
i int;
is_prime bool;
rational_part text;
done int := 0;
repeating_part_size int := 0;
repeating_part text;
result_as_text text;
text_array text[];
BEGIN
for current_value IN 1 .. 99999 LOOP
is_prime := true;
-- check if this is prime
for i in 2 .. ( current_value - 1 ) LOOP
if current_value % i = 0 THEN
is_prime := false;
exit; -- terminate this loop
END IF;
END LOOP;
-- avoid inspecting this number if it is not prime
if is_prime = false THEN
continue;
END IF;
result_as_text := ( 1 / current_value::numeric )::text;
i := strpos( result_as_text, '.' );
rational_part := substr( result_as_text, i + 1 );
repeating_part_size := current_value - 1;
repeating_part := substr( rational_part, 1, repeating_part_size );
RAISE DEBUG 'Inspecting % -> % {%} => % ( %, % )',
current_value,
rational_part,
repeating_part_size,
repeating_part,
i,
( 1 / current_value )::text;
text_array := regexp_split_to_array( rational_part, repeating_part );
is_prime := true;
FOREACH result_as_text IN ARRAY text_array LOOP
IF result_as_text <> '' AND substr( repeating_part, 1, length( result_as_text ) ) <> result_as_text THEN
is_prime := false;
exit;
END IF;
END LOOP;
IF is_prime THEN
RETURN NEXT current_value;
done := done + 1;
END IF;
IF done > l THEN
EXIT;
END IF;
END LOOP;
RETURN;
END
$CODE$
LANGUAGE plpgsql;
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