First-class environments. Discuss. ;) (lambda-the-ultimate.org)

I always though it would be cool for a language have a special array-like object called 'scope'. To test if a variable was in scope you would say something like "if 'a' in scope:". It could also be useful in debugging. You could definitely abuse it, like global variables or Javascript's arguments.caller, but with great power comes great responsibility.

  def f():
    x = 1
    if 'x' in locals():
      print 'x in scope'
  
  f()
  x in scope