Re: CONST and VALUE revisited

David,

When calling a procedure, a CONST parameter cannot be changed in the called procedure. There may be some trickery available to do it, but you'd have to work pretty hard to fool the compiler.

The comment "the parameter is not INTENDED to be changed." probably referred to the case when using a prototyped call to a program, via the EXTPGM() keyword. In that case, the caller may specify CONST, but the called program sees the parm as a "regular" parm, meaning by reference.

A VALUE parm can be changed in the called procedure, but the changed value will not be passed back to the caller.

-mark


At 1/28/09 01:09 PM, you wrote:

David wrote:
> I thought I would read in the data area in my main procedure
> and then directly call a subprocedure with CONST on the parameter
> to protect my data area.
> However, from experience I've noticed that it is still possible to modify
> the parameter inadvertently, and we have already discussed this.
> Someone said that CONST in reality only means that the parameter
> is not INTENDED to be changed.

> So, I just thought it was a bit ironic : normally, I use CONST on all
> parameters
> used for input. But now that I REALLY don't want my parameter to be
> changed,
> I shall code VALUE instead.


David -

I have this page bookmarked:
http://www.web400.com/download/ilerpg/subprocedure_parameters2.htm

- sjl