
Another circular program 
the list nums is defined in terms of itself:
let rec
first = lambda n. lambda L.
if n = 0 then nil
else (hd L)::(first (n1) tl L),
nums = 1::(1::(F nums)),
F = lambda L. (hd L + hd tl L)::(F tl L)
in first 5 nums
{\fB Fibonacci List \fP}

F adds the first two numbers on its input L
to form the first element of its output,
which in turn becomes part of the input.
Note that first and F
are quite ordinary functions and could be applied
to many other lists.

window on the wide world:
λ ...
::  list cons 
nil  the [ ] list 
null  predicate 
hd  head (1st) 
tl  tail (rest) 


