An interpreter for the Lambda Calculus

Terms have to have the following form:

\x.M  | Abstraction
(M N) | Application
x     | Variable

Examples

const
\a.\b.a

omega (infinite recursion -> doesn't terminate)
(\f.(f f) \f.(f f))

y-combinator
\f.(\x.(f (x x)) \x.(f (x x)))

addition (on church numerals)
\n.\f.\x.(n (f x))