###predefines for Peter Sestoft's Lambda Calculus reducer http://www.itu.dk/~sestoft/lamreduce/lamframes.html
Nil = (\c.\n.n);
isnil = (\l.l (\h.\t.fal) tru);
Cons = (\h.\t.\c.\n.c h (t c n));
head = \l.l (\h.\t.h) l;
tail = \l.fst (l (\x.\p.pair
(snd p)