RE: RPG IV Pointers

[Colin Williams <colin.williams@xxxxxxxxxxxxxxxxx>]

Why do you think you need two pointers in RPG?

-----Original Message-----
From: Jim Langston [mailto:jlangston@conexfreight.com]
Sent: Wednesday, March 01, 2000 4:33 PM
To: RPG400-L@midrange.com
Subject: Re: RPG IV Pointers


Actually, a null pointer is a pointer that is not "cast".  In C you
"cast" the type of data that the pointer is going to point to.  So,
you can set up a pointer to point to type Char, or type Int, or
whatever, then you can just look at the data by "dereferancing"
the pointer directly.

In RPG, however, all pointers seem to be null pointers (not cast)
so to look at the data you actually do it through a different type
of cast pointer, in our example, MyField.

The way it works in RPG does not go 1 on 1 with C, two different
ways of doing things.  In C, it only requires 1 pointer to do what you
need 2 pointers to do in RPG.  Not necessarily bad, mind you, but
different, and something I just had to understand to be able to use it.

Regards,

Jim Langston

Colin Williams wrote:

> Personally, I like to think of it as a data structure with a pointer
> attached to it, that I can set to any value.
>
> Got some data in a user space, set the pointer to the start 
of the user
> space, and look at the data via the data structure
> Got some data in another data structure, set the pointer to 
the start of
> the other data structure, and look at the other data structure via the
> data structure
>
> Is a null pointer any pointer that has not been set yet?

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