Re: AW: Long Constant Names -- RPG400-L

I like the idea of constants in data structures also.  I have build
command structures where only a few letters of a library name needs to
change in the command, based on the library the prog is dealing with,
i.e.:

     D CmdLine         DS                  Qualified
     D  Chunk1                       12A   Inz('CLRPFM FILE(')
     D  Acronym                       3A   Inz(*Blanks)
     D  Chunk2                       14A   Inz('FILES/TMPFILE)')

In this example, Chunk1 and Chunk2 will never change, hopefully. 
Acronym is the only thing that needs changing.  It would be nice to be
able to specify the two chunks as constant, not have to specify the
lengths, and be confident that these won't be changed.


On Thu, 30 Dec 2004 11:38:56 -0800, Joe Lee <LeeJD@xxxxxx> wrote:
> Yes, but unless I am missing something, this isn't a constant. The value
> of using a constant rather than an initialized variable is that you
> can't accidently change the value of the constant. While with this
> solution you, or someone else later, could accidently change the value
> of one of the days. A somewhat likely example would be something like
> this.
> 
> If     DayOfWeek.Sunday = Today
>    Or DayOfWeek.Saturday = Today;
>   ItsTheWeekend = *ON;
> EndIf;
> 
> Latter someone is changing the program and modifies it to look like
> this.
> 
> If     DayOfWeek.Sunday = Today;
>    DayOfWeek.Saturday = Today;
>   ItsTheWeekend = *ON;
> EndIf;
> 
> Now DayOfWeek.Saturday is no longer 7.
> 
> Joe Lee
> 
> >>> Hauser@xxxxxxxxxxxxxxx 12/30/2004 11:22:56 >>>
> Hi Lee,
> 
> you can do so, if you replace const through INZ and define the field as
> 1S 0
> or 1P 0:
> 
> D DayOfWeek      DS                qualified
> D   Sunday                   1S 0  inz(1)
> D   Monday                   1S 0  inz(2)
> D   Tuesday                  1S 0  inz(3)
> D   Wednesday                1S 0  inz(4)
> D   Thursday                 1S 0  inz(5)
> D   Friday                   1S 0  inz(6)
> D   Saturday                 1S 0  inz(7)
>  *-----------------------------------------
>  /EXEC SQL  :Today = DayOfWeek(Current_Date)
>  /END-EXEC
> 
>  /Free
>    Select;
>    When Today = DayOfWeek.Sunday;
>    When Today = DayOfWeek.Monday;
>    ...
>    EndSL;
>    *inLR = *On;
>  /End-Free
> 
> Birgitta
> -----Ursprungliche Nachricht-----
> Von: rpg400-l-bounces@xxxxxxxxxxxx
> [mailto:rpg400-l-bounces@xxxxxxxxxxxx]Im Auftrag von Joe Lee
> Gesendet: Donnerstag, 30. Dezember 2004 20:03
> An: rpg400-l@xxxxxxxxxxxx
> Betreff: Re: Long Constant Names
> 
> An interesting idea occurred to me while reading this. Would it be
> possible to add constant qualified data structures? These constants
> would be used and defined just like a variable qualified data
> structure.
> So you would have something like the following.
> 
> DayOfWeek     DS                 Qualified Const
>  Sunday                                 Const(1)
>  Monday                                Const(2)
>  Tuesday                               Const(3)
>  Wednesday                          Const(4)
>  Thursday                              Const(5)
>  Friday                                   Const(6)
>  Saturday                              Const(7)
> 
>  /Free
>   Select;
>    When  today = DayOfWeek.Sunday;
>    When  today = DayOfWeek.Saturday;
>   EndSl;
> /End-Free
> 
> This would help avoid the need to have "long" constant names, at least
> in the still fixed format D specs, and provide an easy and consistent
> method of specifying context.
> 
> Would something like this be a "good" thing? And how hard would it be
> to implement, Hans? Barbara?
> 
> Joe Lee
> 
> >>> antoine.contal@xxxxxxx 12/30/2004 08:12:34 >>>
> 
> Steve,
> 
> You're right. In fact, this double semantic load a constant has to
> bear
> is the reason I'm talking about constant names specifically, and not
> variable names in general. Generally speaking, the constant should
> state
> both the context (e.g.,
> 'dayofweek', 'ErrMsg') and the value (e.g. 'monday', 'StUpd').
> 
> I'd rather put an underscore between the two parts, but if I can't
> have
> more than 15 chars, I have to use chars sparingly.
> 
> Regards.
> 
> --
> Antoine CONTAL
> 
> something else to keep in mind is that a constant will 99% of the time
> be one of a set of values.
>    dayofweek_monday
>   dayofweek_tuesday
> 
>   statuscode_active
>   statuscode_held
>   statuscode_deleted
> 
> It follows that the constant name should always indicate that
> relationship. What better way is there than the first half of the name
> is the name of the constant set, the second half is the name of the
> constant within that set? You dont have to use the underscore if you
> dont want to.
> 
> -Steve
> 
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