closures and dynamic binding

[greg]

Hrvoje Niksic wrote:
> Common Lisp behaves similar to Python in this
> regard:
> 
> * (loop for i from 0 to 2 collect (lambda () i))

I wouldn't call the CL loop macro the equivalent of
a for-loop. It's more like a while-loop.

The Lisp equivalent of a Python for-loop would be
to use one of the mapping functions. Then, since
the loop body is a lambda, you get a new scope for
each iteration automatically.

> I don't think it has anything to do with variable leaking out of the
> loop.

That's right, it doesn't. If I were designing a
for-loop from scratch, I wouldn't let it leak, but
that part seems to be necessary for backwards
compatibility.

 > In contrast, Scheme regards
> iteration as a special case of recursion, and R5RS "do" prescribes
> assigning loop variables to "fresh locations" to match what recursion
> normally does.

I'd say it prescribes that because it's useful
behaviour, not because it has anything to do with
recursion.

-- 
Greg