Saturday, October 29, 2011

Rapid Initialization

If you, like me, always write your REXX code beginning with a "signal on novalue" (to prevent the use of uninitialized variables), then you (like me) always want to make sure that all your variables are properly initialized.  Here's a fast way to initialize a whole load of variables WHAM!:

   parse value "0 0 0 0 0 0 0"    with ,
               rpt#   rpt. ,
   parse value ""    with ,
               slist   ltoken  stoken  loadlist   ,
               tag   taglist   ,
   parse value 0   "ISR00000  YES       Error-Press PF1"    with,
               sw.  zerrhm    zerralrm  zerrsm

The first PARSE uses a string of several (many, a whole lot of) zeroes because it's concerned with zeroing-out several counters, among which are 'rpt#' and 'rpt.'.  Note the '.' on the last line to flush any unused zeroes.

Any number of counters can be zeroed in a single PARSE by just adding their names to the list.  If more zeroes are needed in the value-pattern, they are easy enough to add because you never have to count.  Need a few more?  Add another twenty or thirty!

The second PARSE is concerned with variables that need to be blanked-out.  Here, you never have to worry about whether there are enough blanks.  To add another variable-to-be-blanked, just add it to the existing list.

The third PARSE initializes a collection of variables to several different values.  'sw.' is set to '0';  'zerrhm' is set to 'ISR00000';  'zerrsm' is set to 'Error-Press PF1';  &cetera.  PARSEs of this type need to be carefully constructed.

Rather than have each variable assigned its value on a separate line, this technique clusters many assignments together in a compact form that does not distract from reading the code for comprehension, it is at least as fast, execution-wise, as doing them one-by-one, and it's a heckuvalot easier to type.


  1. Les Koehler points out that he prefers (for speed)

    Parse Value copies('0 ',40) with ctra ctrb .

    and that characters like '#', '@', '$', and some others are not valid in ANSI-compliant versions.

  2. It's really awesome.. I want to send an email through Rexx (foreground not in batch mode) How i achieve it .. please help me on this.