Re: circumflex/caret

   From: Ger Hobbelt <[email protected]>


   Note that I have a few reports of 'make check' failing; nothing fatal
   so far; the build should still work for you.


   WARNING: the latest crm114-GerH supports scoped script variables, so a
   particular (ugly) variable instantiation use in scripts won't work any
   longer: see

   http://hebbut.net/Public.Offerings/crm114/crm114-BlameBarack-Branch-preliminary.html#scoped_variables


Whoa!!!!  Interesting!  

I tried something like that but got tied up in knots.  For example:

  isolate (:a:) /Foo!/        # a is of global scope
  call /:capture_func:/
  output /:a: is :*:a:\n/

  :capture_func:
  isolate (:z:) /abcdefghijklmnop/           # make :z: be local
  match [:z:] /...(...).../  ( :: :a: )      # capture :a: into :z:
  return

Now, :a: is attached to the 4th through 6th characters of :z: - but
:z: is now _going away_.  So, what does :a: have?

Second question: are these scoped variables "dynamic" or "static" -
that is, if I call a function with a locally scoped variable a second
time, what is the value of a locally scoped variable?  Is it retained
between calls (i.e. "static", as in C), or is the locally scoped
variable reinitialized from scratch (so DEFAULT values values will
trigger in!)

Third question: if it's really scoped, then there should be a way
to create that local variable as an overlay, so it _keeps_ it's
value on return, like this

   isolate (:a:) /foo/     
   call /:capture_func:
   output /:*:a:/         # should be back to /foo/

   :capture_func:
   isolate (:a:) /bar/
   output /:a:/
   return


This drove me to consider that perhaps we needed four different waus
for a variable to be created:

   isolate   - global scope
   dynamic   - local scope, state lost on RETURN
   static    - local scope, retained state
   match     - global by default, but will flow with dynamic or static.

In which case, doing a DYNAMIC or STATIC on a MATCHed variable
does... what?  Do they create local overlays, in which case the old
(MATCHed) value is restored on RETURN, or does it change the type of
variable so they're erased (for dynamic) or hidden (for static) on
return?

And if it's a MATCH captured variable, are changes made while in the 
subroutine kept in the outer variable, or rolled back on RETURN?

These kinds of questions are why there's not been a mainline release
with that functionality.  The semantics are not trivial.

But your notions make me think more clearly on this again..  (as well
as rethinking multiple-values-return capability... which is yet
another matter, but simpler than this one at least)

   - Bill Yerazunis




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