Re: "guessing" the parameter type.

[Hans Boldt <boldt@xxxxxxxxxx>]

Jon Paris wrote:
>  >> Besides it doesn't fits my needs of retrieving the data type using the
> address of a variable.
>
> I'm afraid that you'll never be able to do that.  The pointer carries zero
> information about the type of data it points to - nor could it.  Think about
> a DS where the first field is numeric.  The DS is character, but it's
> pointer will, indeed must, be identical to that of the numeric field that
> begins the DS.
>
> Do you know of any system where this can be done - I've sure never heard of
> it.  Languages like C "pretend" to have pointers to specific data types, but
> they're just pointers like any other and are interchangeable.

Well, ummm, any half decent dynamic OO language can do this. That 
is, in a dynamic OO language, you deal with object references and 
the objects contain all the information needed to identify the type 
or class of object and all the operations allowed on that object.

Theoretically, of course, you could implement a compiled language 
with that type of capability too. But then you'd also have to pay a 
performance penalty.

In other words, compiled languages like RPG are the way they are in 
order to favor run-time performance. If you want more advanced 
capabilities like self-describing data entities, you have some hard 
choices to make. No one programming language can be all things to 
all people.

Cheers! Hans