Re: Exported Variables (was Long Constant Names) -- RPG400-L


1) Some built in functions won't accept a constant value but require a
variable.  %SUBDT is an example.

Actually, you can use a constant value with %SUBDT, but it has to be coded as a date. For example:

     D COOLDATE        c                   d'2005-01-06'
     D year            s             10I 0

      /free
          year = %subdt(COOLDATE: *YEARS);
          dsply ('Year = ' + %char(year));
          *inlr = *on;
      /end-free

2) Different results from %LEN or %SIZE BIFs.  The constant would give me
the length/size of the constant value.  The variable would provide the
length/size of the variable which would be different than the constant value
stored in that variable.  (are these BIFs resolved at compile time or run
time?


%size() is resolved at compile time, %len() is sometimes compiletime
and sometimes runtime, I think.

I don't see why you would ever care about the size/length of a constant, though.

3) The variable could be used in a LIKE definition. (but if type and length
are not exported then this won't work)

That might be nice -- but having a separate constant for the value, and "template" variable for the LIKE definition doesn't bother me much, and it's probably more efficient on memory.

4) You could pass the variable as a parameter to a subprocedure which
requres a 'by reference' variable.

You can already do that with a named constant if the parameter is defined as CONST. If the parameter's not defined as CONST, you couldn't do it with a constant variable, either! (Because it would allow you to change the value of a constant, thus defeating the whole purpose of making it a constant!)

I'd also like to mention the possibility of Reflection APIs on service
programs if variable type/length were exported (including procedure
variables).  Could do some very interesting things with that API.

That might be nice... especially if it eliminated the need to explicitly code a prototype. That way, you could just code the procedure interface, and not have to deal with maintaining two identical parameter lists for every procedure (Which, frankly, is a pain in the butt.)