MOVE (was: /FREE RPG compiler errors)

[Buck Calabro <Buck.Calabro@xxxxxxxxxxxx>]

>When you see a MOVE stmt, you know that the value 
>of factor 2 is being copied right justified to 
>the result variable.

Here are some very common examples of MOVE/MOVEL which are not simple byte
copy operations.  
c                   move      '00000'       *in(20)
really SETOF 20 (Can you spot the bug?)

c                   move      char10        num5   
really convert the last 5 characters to a number

c                   move      char10        num10  
really convert to number

c                   move      char10        char20 
really "touch the rightmost 10 characters and leave the rest alone"

c                   move      char20        char10 
c                   movel     '-'           char10 
c                   move      char10        char20 
really "Put a '-' in column 11 of CHAR20"

c                   move(p)   char10        char20 
really "Wipe out CHAR20 and put touch the rightmost 10 characters"

Rarely are the names that descriptive.  I usually see something akin to
c                   move      cust          suffix
and then I get to find out that this is really extracting the last three
characters of the customer ID, which nominally looks like "1234567-001".  In
this example, it's really "substring the last three characters" and not a
MOVE at all.

Do I use MOVE?  You bet.  Do I think it's handy?  You bet.  Does it cause
problems?  You bet.  Teaching new RPG people the nuances of MOVE, MOVEL and
MOVEA is clearly the most difficult RPG III task in terms of long-term
understanding.  I routinely see bugs in code that are directly attributable
to a programmer misunderstanding MOVE.  Do I miss MOVE in /free?  Yes I do.
But it won't kill me, even though I don't intend to mix /free and fixed
code.  

Where I'll use /free is in NEW code, like a new subprocedure.  I will NOT
try to convert code a line at a time via some automated tool like Code/400.
If I run across a situation where I need MOVE for one of it's very cool
conversion/extraction/substring functions, I will write a subprocedure in
fixed form that uses MOVE.  A perfect example is my "extract the customer
suffix" above.  I just don't have strong feelings on it, I guess.

>The problem with not including MOVE in /free is 
>that IBM did not provide the ability to write a 
>proc version of MOVE.  What is needed are 
>data pointers in RPG, that is a pointer that also 
>contains the attributes of the data pointed to.  
>Or an OPDESC that actually has a complete set of 
>operand description information.  Or allow programmers 
>to write their own BIFs.

Steve wins big here.  By all means, if Rochester and Toronto could get
together on this one, we'd all be happier campers.  Full OPDESC support
would be such a blessing!  The compiler folks aren't the ones driving that
decision-making process, so complaining to them won't help.
  --buck