Getting around immutable default arguments for recursion

[dpapathanasiou]

> You'll continue to be confused if you use that term. Python already
> has a specific use of the term “immutable”, and it doesn't apply
> here.

I was just following the terminology used in "A Byte of
Python" (which, that particular point aside, is a very good tutorial).

> Better to say: default arguments are part of the function definition
> statement, and are evaluated when the definition is evaluated.

Yes, well said.