Duals

Well, in Egel you can trivially write down variadic functions, like sum shown below.

>> def sum = [ X, Y -> sum (X+Y) | X -> X ]
>> sum 1 2 3 4
10

But is the reverse possible too? Best I got to was this:

>> def un = [ 0 -> 0 | N -> N (un (N-1)) ]
>> un 5
(5 (4 (3 (2 (1 0)))))

I think I need something like a reverse too though I am not sure. Also get the feeling I am reinventing Lisp. Which is a bad idea I guess, Lisp will always be better at being Lisp than Egel will ever be.