fib(0) = s(0).
fib(s(0)) = s(0).
fib(s(s(N))) = fib(s(N)) + fib(N).

dfib(0) = s(0).
dfib(s(0)) = s(0).
dfib(s(s(N))) = dfib(s(N)) + dfib(N) + dfib(N).



X+0 = X.
X+s(Y)=s(X+Y).

3=s(2).
4=s(3).
2=s(s(0)).

0-X = 0.
s(X)-s(Y)=X-Y.
X-0 = X.

p(s(X)) = X.


(fib(p(dfib(dfib(3)))) - dfib(s(fib(s(dfib(3)))))) - dfib(dfib(3)) = 2 -> [].



precedence([dfib,fib,+,-,4,3,2,p,s,0]).