Bad return type in example

* postgresql-9.6-A4.pdf, page 891
* https://www.postgresql.org/docs/9.6/static/xfunc-sql.html#XFUNC-SQL-BASE-FUNCTIONS

Dear Doc Writers,

Would it not be better to change the return type of the following two sample functions to numeric ?

CREATE FUNCTION tf1 (accountno integer, debit numeric) RETURNS integer AS $$
UPDATE bank
SET balance = balance - debit
WHERE accountno = tf1.accountno;
SELECT balance FROM bank WHERE accountno = tf1.accountno;
$$ LANGUAGE SQL;

CREATE FUNCTION tf1 (accountno integer, debit numeric) RETURNS integer AS $$
UPDATE bank
SET balance = balance - debit
WHERE accountno = tf1.accountno
RETURNING balance;
$$ LANGUAGE SQL;

Since debit is of type numeric, balance is (probably) numeric too, so the function ought to return numeric. I guess that the function works as it is using implicit type cast.

With best regards,
Nikolaus Thiel