(* ToDo: This is not efficient. We take the n for the 2^n lower bound fro x>0. This limit can be arbitrarily small and far away from beeing tight. To make this really computational, we need to compute a tight limit starting from scale x and going down in steps of say 16 bits, something which is still easy to compute but likely to succeed. *)
Definition CRealLowerBound (x : CReal) (xPos : 0<x) : Z :=
proj1_sig (xPos).

Lemma CRealLowerBoundSpec: forall (x : CReal) (xPos : 0<x),
forall p : Z, (p <= (CRealLowerBound x xPos))%Z
-> (seq x p > 2^(CRealLowerBound x xPos))%Q.