0 QTRS
f(X) → cons(X, n__f(g(X))) g(0) → s(0) g(s(X)) → s(s(g(X))) sel(0, cons(X, Y)) → X sel(s(X), cons(Y, Z)) → sel(X, activate(Z)) f(X) → n__f(X) activate(n__f(X)) → f(X) activate(X) → X