Re: MOVEA -> EVAL

[boldt@xxxxxxxxxx]

Phil wrote:
>This is an undefined operation in C (right up there with 'array[x] =
x++'),
>and no one reasonably familiar with the language would do it.  I can't
>think of anything off the top of my head, but I would be very surprised if
>RPG were devoid of any statements whose behavior was officially undefined.

Surprise!  Surprise!

Consider the RPG statement "eval x=a+p(a);", where p is a
procedure that takes a reference parameter.  If the procedure
changes the value of the passed parameter, RPG makes no
guarantees regarding the final value of the expression.

To illustrate, consider the following program:

H dftactgrp(*no)
D p               pr            10i 0
D  parm                         10i 0
D a               s             10i 0 inz(1)
 /free
    dsply (%char(a+p(a)));
    *inlr = *on;
 /end-free
P p               b
D p               pi            10i 0
D  parm                         10i 0
 /free
    parm += 1;
    return parm;
 /end-free
P p               e

Does this program display 3 or 4?

Cheers!  Hans

Hans Boldt, ILE RPG Development, IBM Toronto Lab, boldt@ca.ibm.com

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