CUSP = lisp made easy.

Well, I had a good look at CUSP today, and I must admit: it is suspiciously easy to get started and enormous fun to use (for me as an amateur lisp lover). Installation was a breeze (it installs all sbcl on its own. easy!). Up and running in no time.

Respect!

python closure problem

>>> def acc_gen(initial_value):
...   total = initial_value
...   def acc(to_add):
...     total += to_add
...     return total
...   return acc
...
>>> a = acc_gen(5)
>>> a(3)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 4, in acc
UnboundLocalError: local variable 'total' referenced before assignment

I'm shocked! That doesn't make sense to me. Cfr:

[1]> (defun acc-gen (total) (lambda (to_add) (incf total to_add)))
ACC-GEN
[2]> (setf a (acc-gen 5))
#
[3]> (funcall a 3)
8
[4]> (funcall a 3)
11

I'm a little bit clueless, but I'm pretty sure that this is what they mean with "python doesn't support proper lexical closures"