SQL to return all function parameters- its working

Based on replies to another post (recommending use of
'generate_series'), I was able to write the following query that
returns all paramters of a given function.
Only one interesting thing to note- in order to return the proper
argument type, I had to use
proargtypes[i - 1] when I expected this to work: proargtypes[i]

Any feedback would be appreciated...

SELECT n.nspname AS name_space,
p.proname AS function_name,
p.oid AS function_oid, t.typname AS rettype,
p.prosrc AS body,
argument, argument_type
FROM pg_proc p
INNER JOIN (SELECT oid, proargnames[i] AS argument, proargtypes[i-1]
AS argument_type
FROM
(SELECT oid, proargnames, proargtypes,
generate_series(1, array_upper(proargnames,1)) AS i
FROM pg_proc) s
) arg
ON p.oid = arg.oid
INNER JOIN pg_namespace n
ON p.pronamespace = n.oid
LEFT OUTER JOIN pg_type t
ON t.oid = p.prorettype
-- WHERE p.proname = 'func_name'