RE: No Subroutines (was Re: Debugging many subprocedures)

On Wed, 2005-08-03 at 07:46 -0500, Joe Pluta wrote:
> > From: Rich Duzenbury
> > 

> Nitpick: This won't work because the first three return statements will
> be flagged for not returning anything.
Right, as I said "not drawn to scale" -- I didn't compile any of this,
just off the top of my head.

>   But it does bring up an
> interesting class of problems, the "single-error validation routine"
> (SEVR).  In the single-error validation routine, the first error
> encountered causes a failure and the program ends.  As it happens, RPG
> has an absolutely outstanding way to handle that situation:
> 
>  /free
>   select;
>     when parm1 <> 'foo';
>       rc = '*BADPARM1';
> 
>     when parm2 <> 'bar';
>       rc = '*BADPARM2';
> 
>     when parm3 <> 'baz';
>       rc = '*BADPARM3';
> 
>     other;
>       rc = '*OKAY';
>       // do the magic here
>   endsl;
> 
>   // now return the result
>   return result;
>  /end-free
> 
> Not a lot of people think of using select this way, especially Java
> programmers, because in most languages the "switch" statement is the
> closest analogue, and switch supports only comparing a single value.
> Because you can have complex comparisons on every when, the select
> statement is much more powerful and lends itself quite nicely.

Hmm, it does work, but seems a bit 'tricky' to me.  Some maintenance
programmers I know would look at that select and say to themselves -
"hey, these select clauses don't do anything.  I can delete them."

> 
> BTW, the MEVR (multiple-error validation routine) is better handled
> using if statements.  Typically an MEVR returns a Boolean (good/bad); it
> calls a routine to log each error in some way.
> 
> /free
>   valid = *on;
> 
>   if parm1 <> 'foo';
>     sendError('Parm 1 Error');
>     valid = *off;
>   endif;
> 
>   if parm2 <> 'bar';
>     sendError('Parm 2 Error');
>     valid = *off;
>   endif;
> 
>   if parm3 <> 'baz';
>     sendError('Parm 3 Error');
>     valid = *off;
>   endif;
> 
>   if valid;
>     // do the magic here
>   endif;
> 
>   // now return the result
>   return valid;
>  /end-free
> 
> Joe
> 

This looks excellent.  Easy to read and easy to understand.  


Regards,
Rich