#!/usr/bin/env ruby
# This code comes from http://ruby-it.org/pages/Closure+in+python
# Check the page for copyright notice and explanations



 >>> def esponenziale(n):
 ...  lambda a: n=n*n
 ...
   File "<stdin>", line 2
 SyntaxError: can't assign to lambda

>>> def square_generator(num):
...  def f():
...   return num * num
...  return f
...
>>> square2=square_generator(2)
>>> square2()
4

>>> def exp(num):
...  def f():
...   num= num * num
...   return num
...  return f
...
>>> potenze=exp(2)
>>> potenze()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "<stdin>", line 3, in f
UnboundLocalError: local variable 'num' referenced before 
>>> def exp(num):
...  ary=[num]
...  def f():
...   ary[0]= ary[0]**2
...   return ary[0]
...  return f
...
>>> square=exp(2)
>>> square()
4
>>> square()
16