Re: Special variables to relax boxing

[Stefan Israelsson Tampe]

Hi guiler, Hi Daniel.

I lost this thread in my mail application, sorry, so I try to continue
this way instead.

* This feature for scheme is mainly for macro writers which knows what 
  they are doing and which only guard state varibles not seen to the 
  application programmer. This is how I use this feature in guile-log 
  so it will not change how most people need to reason about scheme, the 
beuty 
  remains. It makes insanly difficult tasks possible and simple things
  works as before.

* I really like guile to cater for advanced users. Not only
  noobs. Although we should hide this feature really deep and put some
  serious warnings in the documentatin about the use. I actually hate
  using set! and if you look at e.g. guile-syntax-parse you will see
  that I rewrote everything with let loops, e.g. I really prefere that
  way of looping. I do understand your worry to let people loose on
  writing set! heavy code - that is not scheme. I also ported common
  lisp code to scheme and It was a horrible experience to see all set!
  ing in the code and I just had to rewrite quite a lot of the common
  lisp with rewriting the loops. But then a new version comes out and
  you are smoked.

* If we are serious about combining emacs-lisp with guile we should
  really aim to have this feature added with deep support. The reason is 
that
  using set! in lisp world is a style of programming and is very
  common. For this reason I don't expect much emacs-lisp to combine
  well with undo redo additions via prompts. This hearts me really
  hard because it would be so cool to be able and schime in to a
  emacs-lisp project, add  a few lines of code and show of a well 
  functioning redo and undo addition to the complex emacs lisp code - 
  this would be a really good selling point for guile-emacs and as I
  said, I hate that we don't have a nice support for it.

* The proposed semantics piggy packs ontop of fluids sematics so
  everything we have done incorporating fluids carry over directly to
  special variables. And the extra stuff is really not that
  much. E.g. the maintainance burden is probably much less that your
  perception of it.

* We need 2 extra VM op's if we are serious ablut implementing this
  though but they are simply essentially a copy paste of the fluid
  code so one could factor out the code somewhat. Another possibility
  is to add an option to the current fluid vm ops.

* If you don't redo and undo nothing in the way scheme works changes
  it's only when you undo and redo stuff that the semantics becomes 
  important.

I really think that this is an important addition of guile and it would
really be a dissapointment not having it's support considering the
great gain you can get via optimizations with really not much extra
work in guile. Also I think that I managed to get the semantics and
implementation in a really beutiful state where a lot of effort have
been in making it mix well and be consistant in what it does and
actually get it into a state where it _is_ much simpler to reason
about the code considering other way's of implementing the 
optimisations.
Albait more difficult than before.

Have fun
/Stefan