Y combinator

Y.coffee

# The common one, converted to CoffeeScript
y = (f) -> ((y)-> y y) (y) -> f (n) -> (y y) n

# My version
y = ((y)->y y) (y) -> (f) -> (n) -> (f (y y) f) n

fact = y (f) -> (n) -> if n is 0 then 1 else n * f n-1

# And a simpler way, requires a different `fact` that passes itself to itself
y = (f) -> (n) -> (f f) n
fact = y (f) -> (n) -> if n is 0 then 1 else n * (f f) n-1