Lambda calculus

I have written a small introduction to untyped lambda calculus.

The article contains nothing new, but it has been written to be easy to understand. The article is not only elementary. It contains all essential results of untyped lambda calculus like the Church Rosser theorem and some undecidability theorems.

I have tried to use graphic notations to make the content more digestible and closer to intuition. I am especially proud of the proof of the Church Rosser theorem which (hopefully) is more understandable in this article than in many other presentations I have read so far.