Re: %TLOOKUP

[Hans Boldt <boldt@xxxxxxxxxx>]

Mark: Yes, ALT can be used with arrays. How would I code an 
"associative array" without using tables? Probably something like:

   monitor;
      char = TypeChars(%lookup(SrcAttribute:SrcTypes));
   on-error 121;
      char = '-';
   endmon;

As you can see, the above code avoids the use of a separate index 
variable. But then, I don't see what's the big deal about avoiding 
an index variable. Either way, there's still only one lookup.

(BTW, there are several languages available that properly implement 
the concept of "associative array". Rexx, Perl, and Python (among 
others) allow the use of any string as an index. In Rexx, any 
there's no difference between a associative arrays and normal 
arrays. In Perl, they're called "hashes", and in Python, they're 
called "dictionaries". In whatever language, it's a very powerful 
and popular concept.)

Cheers! Hans


mlazarus@xxxxxxxx wrote:
> Hans,
>
>
> > I understand what you're saying. It's just that we suspect that 
>
> tables are relics of an older era, and that there's not much need to 
> do much with them. Functionally, there's nothing that you can do 
> with tables that you can't also do with arrays. And since arrays are 
> so much more powerful anyways, why bother limiting yourself by using 
> a table?
>
>
> > On the other hand, if there really is some overwhelmingly compelling 
>
> reason that tables should be enhanced, I'm all ears!
>
>  One word: "simplicity".
>
>  I'll say at the outset that if I were designing the language from the
> ground up, there would be no diference between a table and an array.  But
> since there is this concept built into the language, I may as well use it. 
>
>  I recently had occasion to use it, so it's fresh in my mind.  I have a
> simple compile time table with static data that contains the "columns":
> Source type, Type code and Description.  Source type is unique.  Type code
> can repeat and Description will be ignored by the program (it's only for
> the programmer's edification.)
>
>  The requirements are simple:  If it's found in the table, use the
> alternating table's value.  So the code looks like this:
> IF   %TLookup( SrcAttribute: TabSrcTypes: TabTypeChars ) = *Off  ;
>   RETURN  '-'                                                    ;     
> ELSE                                                             ;     
>   RETURN  TabTypeChars                                           ;     
> ENDIF                                                            ;     
>
>  With arrays this would require a separate lookup, an additional variable
> (the index), code to reset the index.  It's not a large amount of code
> difference, but it is slightly more complex.
>
>  Can the ALT keyword be used w/ compile time arrays?  (I still want to keep
> the values side-by-side on the bottom.)  If not, then I would have to
> define it as an OVERLAYed DS, but it would still require using an index
> variable; not as elegant.