RE: Parameter prototype question

-----Message d'origine-----
De : rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] De la part de Simon Coulter
Envoyé : vendredi 14 mai 2010 09:22
À : RPG programming on the IBM i / System i
Objet : Re: Parameter prototype question


On 14/05/2010, at 4:06 PM, David FOXWELL wrote:

Well, now I'm wondering about the value of using CONST at

all. I don't

see that that's much protection against anything unless you don't
test. It seems we only really need it to indicate which

parameters are

intended to be used as input only. The kind of problem I've had
without using CONST could be waiting to happen in many other
procedures.

Pah! The compiler can't protect you from stupidity. The
problem was caused entirely by you trying to stuff 9 pounds
in a 7 pound bag and not expecting it to overflow i.e., not
paying attention to what you were doing. Sure, without CONST
or VALUE the compiler would have caught the mismatch but
consider the reverse situation where you might want to pass a
smaller value or a different data type or a literal; in all
these cases the compiler will assist you by verifying the
base data type (i.e., numeric vs. character vs. date) is
correct and will convert the actual type to the expected
type. This makes the procedure far more flexible and useful
than forcing the consumer to define an exactly matching data type.

Note that you would have received exactly the same error if
you'd tried an arithmetic EVAL that resulted in a value too
large for the variable e.g. small = EVAL
some-bloody-huge-arithmetic-expression. Do you expect the
compiler to protect you from that situation too? Both of
these cases are run-time errors for which proper exception
handling can be implemented to at least catch and notify you
of the problem.

Regards,
Simon Coulter.
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