🚀 go-pugleaf

In <1993Jan24.181958.6740@athena.mit.edu> The Rottweiler writes:
>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
>
> [ rest of program deleted ]
>My question is simple - is this a bug or a limitation of the
>Rexx programming language?  Or is it that I'm doing something
>wrong?
>
>                            Jake

I am not sure if this is a REXX "limitation", or a part of the
definition of the language but I believe that you may not perform
an instruction as part of a "while" statement.  While this is
legal in C, and is "do the assignment to 'n', and compare with '0'"
every "=" inside the parentheses of a "while" is considered the
logical "equals?" symbol.

Here is a trick that is little known to OS/2 REXX programmers, the
"trace ?i" instruction.  Add to the second line of you program,
just after the /* */ and then you have an interactive debugging
environment - you can issue REXX commands such as 'say', or any
variable assignments (i.e. change the value of a variable, or
create a new one), or you can issue any OS/2 command (e.g. DIR,
start epm foo.c, etc.).
  It is most powerful and well known to CMS REXX programmers, yet
it takes a while for the word to spread to new REXX systems.  Use
the 'trace' command.
Cheers,
Martin Lansche, IBM PRGS Canada Lab, Toronto

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