Re: how to let my program sleep a while

["paul cunnane" <paul@xxxxxxxxxxx>]

> ok, this is the place I usually start getting lost when trying to maintain
> this new stuff.  What are you doing, and what is the advantage?  Are these
> added lines of code just to prevent having to define a field as *HMS in a
> prototype?

I guess this is the result of topic drift.

Here's where I was going with the symbolic constants: there was a
suggestion, deprecated by Barbara, to use a parameter to identify whether
the sleep was 'for' or 'til' -- I think it may have been you who suggested
it, Booth.  Let's pretend for a second that we are still using that method.

If you simply use string literals, there is a danger that the wrong string
will get passed into the procedure.  For example, after several hours of
coding, I do something daft like pass 'ti1' instead of 'til' -- note that I
accidentally substituted the digit 'one' for the lowercase 'l'.  The results
of this are unpredictable; they depend on how the procedure handles the
argument.  If, for example, it uses the logic

 if     type = 'til'
  (do something)
 else
  (do something else)
 endif

you will get the 'for' logic unexpectedly.

The answer I use is to code symbolic constants, which by convention in many
languages are represented by all uppercase variable names.  The examples I
gave were FOR and UNTIL, to which I assigned constant values of 0 and 1,
respectively.  Note that these are now numeric variables.

The procedure uses these constants exclusively:

 if     type = UNTIL

which is exactly equivalent to

 if     type = 1

only clearer.  The calling program uses the same constants, and everybody is
happy.  We even get some compile-time checking: if I mis-spell UNTIL, the
compiler will complain about an undeclared variable.

The question remains, how do we make sure that the caller and the callee use
the same constant names to mean the same thing?  This is where the /COPY
member comes in.  The source containing the procedure includes the /COPY, in
order to include the prototype for the procedure.  The calling program uses
the same /COPY member.  This makes it the ideal place to store the
constants.

Again, Barbara correctly pointed out that it was more appropriate to use two
procedures in this case.  There are other situations where this is not so,
and for these I would use symbolic constants.

Did all this help, or just confuse the issue further?

--
Paul


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