What's better about Ruby than Python?
adalke at mindspring.com
Thu Aug 21 19:00:44 CEST 2003
> Lisp hashtables can key off any Lisp datum, but...
Bear with my non-existant Lisp knowledge
Suppose the code is modified. How does the hash table
get modified to reflect the change? Written in Python,
if I have
a = (1, 2, (3, [4, 5]))
I can't hash it because someone could come by later
so the hash computation and test for equality
will give different results.
> The next step would
> have been to determine when the closure had best re-execute the code
> body to see if the world had changed in interesting ways, but that is a
> big step and requires dependency tracking between cells.
Ahhh, so the Python code was comparable in power without
> Once a Cell is told an input has changed, it re-runs its body to see if
> it comes up with a different result, in which case it caches that and
> tells other dependents to rethink their caches.
Err, or maybe not. I don't see how this is done in the Lisp
code. Still, such flexibility is available in Python without
recourse to macros.
> So what is shown in my example is fun but halfbaked. I was just trying
> to show how a macro could hide the plumbing of an interesting mechanism
> so the reader can focus on the essence.
Could the same code be written in Lisp using an approach
like I did for Python? How would a non-macro solution look
like? What's the advantage of the macro one over the non-macro
one? Just performance?
dalke at dalkescientific.com
More information about the Python-list