Definition semax_equiv {CS: compspecs} {Espec: OracleKind} c1 c2: Prop := forall Delta P Q, semax Delta P c1 Q <-> semax Delta P c2 Q.

Lemma unfold_Ssequence_sound: forall {CS: compspecs} {Espec: OracleKind} c, semax_equiv (fold_Ssequence (unfold_Ssequence c)) c.