Definition CReal_opp (x : CReal) : CReal :=
{|
seq := CReal_opp_seq x;
scale := CReal_opp_scale x;
cauchy := CReal_opp_cauchy x;
bound := CReal_opp_bound x
|}.
Notation "- x" := (CReal_opp x) : CReal_scope.
Definition CReal_minus (x y : CReal) : CReal
:= CReal_plus x (CReal_opp y).
Infix "-" := CReal_minus : CReal_scope.

Lemma CReal_plus_proper_l : forall x y z : CReal,
CRealEq x y -> CRealEq (CReal_plus z x) (CReal_plus z y).