Lisp refactoring puzzle

[Roy Smith]

In article <4E1CF936.4050902 at canterbury.ac.nz>,
 Gregory Ewing <greg.ewing at canterbury.ac.nz> wrote:

> Xah Lee wrote:
> > they
> > don't provide even simple list manipulation functions such as union,
> > intersection, and the like. Not in perl, not in python, not in lisps.
> 
> Since 2.5 or so, Python has a built-in set type that
> provides these (which is arguably a better place for them
> than lists).

Set is the best addition to Python since string methods.