Re: Advantages of RPG

[Joe Pluta <joepluta@xxxxxxxxxxxxxxxxx>]

Doug Palme wrote:
> your statement of "perhaps the best 
> implementation ever..." are you referring to the SELECT statement 
> specifically or the group as a whole?  The reason I ask is that 
> SELECT-ENDSL is the same as SELECT CASE-END SELECT is it not?
>
> If I am off the mark on this, please feel free to correct me.
>   
Not a correction so much as a clarification.  Most implementation of 
CASE logic have actually been variations on the SWITCH statement.  The 
concept of a switch is that you have a single variable, and then you 
execute logic based on the contents of that variable.

  switch (a) {
    case 1: doSomething1();
       break;
    case 2: doSomething2();
       break;
    default;
       doSomethingElse();
  }

SELECT on the other hand was much more a derivation of the old CASE 
construct in RPG, where you could compare any two variables.  And in 
RPG, a combination of SELECT and procedures is incredible:

 SELECT;

    // Opcodes 01 and 02 don't need authorization
    WHEN OPCODE = '01';
        DoOpcode1();
    WHEN OPCODE = '02';
        DoOpcode1();

    // Opcode 10 needs authorization
    WHEN not Authorized();
        SendError('Not Authorized');
    WHEN OPCODE = '10';
        DoOpcode10();

    // Bad opcode
    OTHER;
        SendError('Bad Opcode');
  ENDSL;

The code above is just stunningly simple for client/server programming.  
I used this all throughout the RSDC Scheduler application and I was able 
to create new servers in minutes.  The fact that the WHEN can be as 
complex as you need it, or even execute a subprocedure (which in turn 
could call another program!) makes this one of the very best opcodes 
ever designed for procedural logic.

Joe