0 = \ f x . x;
1 = \ f x . f x;
2 = \ f x . f ( f x );

isZero = \ n . n (\ x . false) true;
succ = \ n f x . f ( n f x );
pred = \ n f x . n (\ g h . h ( g f )) (\u . x) (\u . u);
add = \ m n . n succ m;
sub = \ m n . n pred m;
mul = \ m n f . m ( n f );
exp = \ b n . n b;

main = add 2 1;