Module Proof3.  (*************** inductive lseg *******************)
Fixpoint lseg (sh: share)
(contents: list val) (x z: val) : mpred :=
match contents with
| h::hs => !! (x<>z) &&
EX y:val,
data_at sh t_struct_list (h,y) x * lseg sh hs y z
| nil => !! (x = z /\ is_pointer_or_null x) && emp
end.
Arguments lseg sh contents x z : simpl never.
Hint Resolve lseg_local_facts : saturate_local.
Hint Resolve lseg_valid_pointer : valid_pointer.

Lemma lseg_cons': forall sh (v u x a b: val) ,
readable_share sh ->
data_at sh t_struct_list (v, u) x * data_at sh t_struct_list (a,b) u
|-- lseg sh [v] x u * data_at sh t_struct_list (a,b) u.