Re: CONST and VALUE revisited

[Vern Hamberg <vhamberg@xxxxxxxxxxx>]

I'm replying to several posts after this one -

If the prototype for a procedure has CONST on a parameter, the PI for it 
also has to have CONST - the compiler will not allow you to have a mismatch.

I suppose *ENTRY PLIST suffers from the lack of data checking that it 
always has. That is why I prefer to use a prototype and PI for the main 
procedure.

Now I don't remember putting CONST on a parameter to the main procedure 
- that's an interesting thought. Nor have I put VALUE on that.

OK - just did that kind of thing - here is a listing message when I 
tried to use VALUE - yes, it is maybe intuitively obvious that this is 
not possible, but hey, it's almost 7pm!

RNF3769 30 a      000600  The main procedure cannot use parameters 
passed by value.

The use of CONST there IS acceptable, because that is still a pointer. 
CALL to a program cannot use by-value - only by-reference.

Now can one directly modify a CONST parameter in the main procedure? 
Let's see!!

Nope!!

RNF5346 30 a      000900  Result of EVAL operation must not be a field 
that cannot be modified.                                                 

Hope that is helpful and useful in understanding CONST and VALUE a 
little bit more.

Time to go home or go eat!
Vern

Jeff Young wrote:
> Based on that info, CONST is enforced by the compiler ONLY if you are using sub-procedures.
> If you are using an external service program or just another program, then using VALUE is the only way to ensure that the parameter will not be changed on return from the call.
>
> Is this a correct summary?
>
> Thanks,
>
> Jeff Young 
> Sr. Programmer Analyst
> IBM -e(logo) server Certified Systems Exper - iSeries Technical Solutions V5R2 
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