Fixpoint DDcut_limit_fix (upcut : DedekindDecCut) (r : Q) (n : nat) :
Qlt 0 r
-> (DDupcut upcut (DDlow upcut + (Z.of_nat n#1) * r))
-> { q : Q | DDupcut upcut q /\ ~DDupcut upcut (q - r) }.

Lemma sig_lub :
forall {R : ConstructiveReals} (E:CRcarrier R -> Prop),
sig_forall_dec_T
-> sig_not_dec_T
-> (exists x : CRcarrier R, E x)
-> (exists x : CRcarrier R, is_upper_bound E x)
-> { u : CRcarrier R | is_lub E u }.