Re: variable binding

[Keisuke Nishida <kxn30 at po dot cwru dot edu>]

Jost Boekemeier <jostobfe@calvados.zrz.TU-Berlin.DE> writes:

> [
> (define (foo) +) 
> (foo) 
> (define + -) 
> (foo) 
> doesn't work correctly in the current module system]

> Because Aubrey's evaluator replaces every symbol by a pointer to the
> location (not a pointer to a pointer to a location, which would be
> correct!) the code must examine every memoized expession and unmemoize
> the pointer back into the original symbol.  
> 
> That's why the new module system really needs a new evaluator.  [among
> other things ...] :)

Aha.  Are you designing the new module system in the way that uses a
pointer to a pointer to a location, as you illustrated by symbol ->
variable -> location -> value?  In this case, variables will be memoized
and correct locations will be accessed at run-time.

Although it will be slower than the current model, I think it is okay
because 1) it is simpler and more flexible 2) top-level variable access
is relatively rare so it won't slow down the system significantly.