🚀 go-pugleaf

>I'm doing a little Rexx programming and came upon the following:
>/* */
>
>line = "prpipgphptp"
>
>do while((n = pos("p", line)) \= 0)
> line = overlay(" ", line, n)
>end
>
>say line
> ...
>The output when this program is run is the following:
>
>prpipgphptp
>...

The construct
   do while((n = pos("p", line)) \= 0)
while legal, probably doesn't do what you want it to.  It compares
the variable "n" with the value of the pos() function call.  The
resulting comparison (whose value is 0 or 1) is compared to 0.

Basically, rexx has no assignment operator that can be used within
expressions (like C does).  Your second try is the way to do it.

When in doubt, insert a 'trace ?i' line at the top of your program
and you'll see all the gory details of statement evaluation.  An
example follows:

     4 *-* line = "prpipgphptp"
       >L>   "prpipgphptp"
       +++ Interactive trace.  TRACE OFF to end debug, ENTER to continue

     6 *-* do while((n = pos("p", line)) <> 0)
       >L>   "N"
       >L>   "p"
       >V>   "prpipgphptp"
       >F>   "1"
       >O>   "0"
       >L>   "0"
       >O>   "0"

    10 *-* say line
       >V>   "prpipgphptp"
   prpipgphptp


If still in doubt, comp.lang.rexx is the best place to get answers
regarding rexx in general.

Patrick Mueller                  addr:  pmuellr@vnet.ibm.com
IBM Cary, North Carolina         phone: 919-469-7242