Usefulness of the "not in" operator

[Alexander Kapps]

On 10.10.2011 19:29, Nobody wrote:
> On Sun, 09 Oct 2011 02:25:27 +0200, Alexander Kapps wrote:
>
>> Even if it's off-topic, could you add some similar explanations for
>> Church numerals (maybe Lambda calculus it isn't too much?)
>
> The Church numeral for N is a function of two arguments which applies its
> first argument N times to its second, i.e. (f^N)(x) = f(f(...(f(x))...)).

[SNIP]

Thanks! That's a lot more understandable than Wikipedia. Some 
brain-food for the winter. ;-)