I love this, but it's an awful lot of complexity to print '9' to stdout. The first time I ran it through a python interpreter, I thought I made a mistake.

I bet you think computing prime numbers with Church Numerals is complex too! :)

See, this is why I love this place so much. I'd never heard of Church Numerals before. From the wikipedia entry:

>Many students of mathematics are familiar with Gödel numbering members of a set; Church encoding is an equivalent operation defined on lambda abstractions instead of natural numbers.

Utter clarity. Or, at least as clear as the python code the original post points to :-)

go out and buy Godel, Escher, Bach: Eternal Golden Braid. Right now!

It will make your life better.

I've always meant to pick that up. Looks like google books has a decent online copy:

http://books.google.com/books?id=aFcsnUEewLkC&dq=godel+e...

I had a buddy of mine in highschool who used to bring that book with him every time we took LSD. Of course, he's now got his Ph.D. in physics from Purdue.