the use of 'out' in a parameter list / situation

[Phil Hepburn]

Hi guys,

Can anyone please suggest some X# syntax to show how to use the 'out' option in a parameter list.

I had a quick fumble around but with no good results.

End of day, brain hurts, nee my Forum colleagues ;-0)

Apparently Tuples can happily replace the use of 'OUT'.

HELP !!!

TIA,
Phil.

[lumberjack]

Phil,
Is that not REF?

Code: Select all

METHOD SyMethod(in AS STRING, out REF STRING)

Johan

[Phil Hepburn]

Hi again,

Having had another end of day fumble, I think I have a start, you know, my foot in the door!

Here are a couple of small images :-

Out_01.jpg (23.68 KiB) Viewed 583 times

Out_02.jpg (30.3 KiB) Viewed 583 times

I got success once I stopped trying to include 'as'.

Have a nice weekend,
Phil.

[Phil Hepburn]

Hi Johan,

I am not sure, I thought the REF idea was out of fashion a while back. These sorts of things are no much in my experience.

However, I do like the Tuple (sexy way) I will need to experiment.

I will feed back here if I get anything useful.

Regards,
Phil.

[robert]

Johan,

See https://www.xsharp.eu/help/parameters.html

Code: Select all

parameterList      : LPAREN (parameter (COMMA parameter)*)? RPAREN
                   ;
 
parameter          : (attributes)? SELF? identifier (ASSIGN_OP expression)? (parameterDeclMods datatype)?
                      | ELLIPSIS
                   ;
 
parameterDeclMods   : (AS | REF | OUT | IS | PARAMS) CONST?
                   ;

So AS, REF, OUT, IS and PARAMS are mutually exclusive.

Robert

[lumberjack]

Thanks Robert,

Sorry for any confusion, responded and then only checked the manual and did see OUT is recognized.

The same effect can be "simulated" with REF, provided you initialize the parameter before passing, which the OUT does not require. Both have its place.

REF: The parameter might be changed by the called method.
OUT: The parameter has to be set by the called method.

Regards,

Johan

[Phil Hepburn]

An interesting short post Johan,

Thanks, I will now give these ideas a go in a test 'rig'.

Speak soon,
Phil.

[Frank Maraite]

Hi Johan,
this

REF: The parameter might be changed by the called method.
OUT: The parameter has to be set by the called method.

wasn't clear to me. Thanks!

Does this mean OUT parameters are always NULL at the beginning and should be tested !NULL before return?

Frank

[lumberjack]

Hi Frank,

this wasn't clear to me. Thanks!
Does this mean OUT parameters are always NULL at the beginning and should be tested !NULL before return?

No, it will raise an error during compilation that the parameter is not set.

Code: Select all

FUNCTION TestOut(h AS STRING, w OUT STRING) AS STRING
RETURN h + " " + w
error XS0177: The out parameter 'w' must be assigned to before control leaves the current method

Regards Johan

[Phil Hepburn]

Hi guys - Johan, Frank, and any others interested,

Attached are a couple of small images to help show the functionality etc.

OUT must change in the method code, and REF can change but does not have to. That's how it seems to me.

I suggest you try these out carefully for yourself before you use them, any guy who is not familiar with their use. Just so you know what is going on - check below :-

REfOut_01.jpg (26.59 KiB) Viewed 585 times

REfOut_02.jpg (42.4 KiB) Viewed 585 times

REfOut_03.jpg (36.63 KiB) Viewed 585 times

RefOut_04.jpg (42.49 KiB) Viewed 585 times

RefOut_05.jpg (40.91 KiB) Viewed 585 times

Hope this interests a few of you ;-0)

Cheers,
Phil.