Record ret_assert : Type := {
RA_normal: environ->mpred;
RA_break: environ->mpred;
RA_continue: environ->mpred;
RA_return: option val -> environ->mpred
}.

Lemma modifiedvars_Ssequence c1 c2 id: modifiedvars (Ssequence c1 c2) id <-> modifiedvars c1 id \/ modifiedvars c2 id.